Radio frequency processing apparatus and method

ABSTRACT

In an embodiment, an apparatus includes a radio frequency (RF) generator that is to generate a RF signal, first and second electrodes, and an impedance match module in series between the RF generator and the first electrode. The RF generator detects reflected power from the RF signal applied to a load electrically coupled between the first and second electrodes to change a temperature of the load, the RF signal to be applied to the load until the reflected power reaches a particular value.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 62/372,612, filed Aug. 9, 2016, the entire disclosure ofwhich is hereby incorporated by reference herein.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Unless otherwiseindicated herein, the materials described in this section are not priorart to the claims in this application and are not admitted to be priorart or suggestions of the prior art, by inclusion in this section.

Materials may be processed using different techniques depending on thetype of material, desired end product, quantity of material, energyconstraints, interim control constraints, cost constraints, and thelike. For example, for biologic material, and in particular, foodmaterial, processing may comprise causing food material to be heatedusing RF energy. While frozen food material may be placed in an area ofhigher temperature (e.g., from freezer to refrigerator) to passivelyheat over time, such process may require too long a time period, the endproduct may be non-uniform, and/or the end product have otherundesirable characteristics.

Conversely, frozen food material may be actively heated using, forexample, radio frequency (RF) heating techniques. An example RF heatingtechnique may comprise heating the food material at high frequencies,such as frequencies of 13.56 MegaHertz (MHz) to 40.68 MHz. Using suchhigh frequencies, however, may result in lack of uniformity in theheating due to low penetration depth of high frequency radiation.Another example RF heating technique may be implemented using largevacuum tube systems operating at 27 MHz. In such systems, the vacuumtubes may comprise a free running oscillator having a frequency rangewhich may deviate from 27 MHz and may also deviate from FederalCommunications Commission (FCC) frequency requirements. Performancecharacteristics (e.g., power characteristics) of vacuum tubes also tendto degrade as soon as they are put into operation, with vacuum tubelifespans lasting on average a mere two years. Such vacuum tube systemsmay also operate at several thousand volts, which raise safety concernfor nearby personnel, especially since these systems operate in anenvironment where water or moisture may be present. In other example RFheating techniques, the direct current (DC) to RF power efficiency maybe 50% or less.

Accordingly, processing techniques which address one or more ofpersonnel safety concerns, uniformity in the state of the end product,power efficiency, processing control, compact system size, lower energyrequirements, system robustness, lower cost, system adjustability,and/or the like may be beneficial.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

In some embodiments, a system includes a plurality of radio frequency(RF) generators; a plurality of impedance match modules; a plurality ofelectrode plates, first and second impedance match modules of theplurality of impedance match modules electrically coupled betweenrespective first and second RF generators of the plurality of RFgenerators and respective first and second electrode plates of theplurality of electrode plates; and a conveyor including a groundelectrode. When a load at a start temperature is to be placed on theconveyor, the system uses RF signals generated by the plurality of RFgenerators to cause the load to be at an end temperature different fromthe start temperature, wherein the conveyor is to position the load toelectrically couple to the first electrode plate during a first timeperiod and the first impedance match module is associated with a firstrange of temperatures between the start and end temperatures, andwherein the conveyor is to position the load to electrically couple tothe second electrode plate during a second time period and the secondimpedance match module is associated with a second range of temperaturesbetween the start and end temperatures that is different from the firstrange of temperatures.

In some embodiments, a method includes positioning a load toelectrically couple with a first electrode plate for a first timeperiod, wherein a first impedance match module is electrically coupledbetween the first electrode plate and a first radio frequency (RF)generator, and wherein the first impedance match module is associatedwith a first range of temperatures between a start temperature and anend temperature associated with the load; applying a first RF signal tothe load for a portion of the first time period during which the load isat a temperature within the first range of temperatures, the first RFsignal comprising a RF signal generated by the first RF generator andimpedance matched by the first impedance match module; positioning theload to electrically couple with a second electrode plate for a secondtime period, wherein a second impedance match module is electricallycoupled between the second electrode plate and a second RF generator,and wherein the second impedance match module is associated with asecond range of temperatures between the start and end temperaturesdifferent from the first range of temperatures; and applying a second RFsignal to the load for a portion of the second time period during whichthe load is at a temperature within the second range of temperatures,the second RF signal comprising another RF signal generated by thesecond RF generator and impedance matched by the second impedance matchmodule.

In some embodiments, an apparatus includes means for positioning a loadto electrically couple with a first electrode plate for a first timeperiod, wherein a first means to match impedance is electrically coupledbetween the first electrode plate and a first radio frequency (RF)generator, and wherein the first means to match impedance is associatedwith a first range of temperatures between a start temperature and anend temperature associated with the load; means for applying a first RFsignal to the load for a portion of the first time period during whichthe load is at a temperature within the first range of temperatures, thefirst RF signal comprising a RF signal generated by the first RFgenerator and impedance matched by the first means to match impedance;means for positioning the load to electrically couple with a secondelectrode plate for a second time period, wherein a second means tomatch impedance is electrically coupled between the second electrodeplate and a second RF generator, and wherein the second means to matchimpedance is associated with a second range of temperatures between thestart and end temperatures different from the first range oftemperatures; and means for applying a second RF signal to the load fora portion of the second time period during which the load is at atemperature within the second range of temperatures, the second RFsignal comprising another RF signal generated by the second RF generatorand impedance matched by the second means for matching impedance.

In some embodiments, a device includes a first capacitor in parallelwith an inductor; primary windings of a transformer in series with thefirst capacitor and the inductor; and a second capacitor in series withsecondary windings of the transformer, wherein a radio frequency (RF)input signal is applied to the first capacitor and the primary windingsof the transformer outputs a RF output signal, and wherein an impedanceassociated with the device is to match an impedance associated with aload in series with the device.

In some embodiments, an apparatus includes a first capacitor in parallelwith an inductor; primary windings of a transformer in series with thefirst capacitor and the inductor; and a second capacitor in series withsecondary windings of the transformer, wherein the primary and secondarywindings comprise flat conductive strips, and the transformer comprisesthe primary windings wound around an outer circumferential surface of atube and the secondary windings wound around an inner circumferentialsurface of the tube.

In some embodiments, a method includes changing capacitance of one orboth of first and second capacitors included in an impedance matchmodule in series between a radio frequency (RF) generator and a load,wherein the change is initiated in accordance with a first reflectedpower level, and wherein the first capacitor is in parallel with aninductor, primary windings of a transformer is in series with the firstcapacitor and the inductor, and the second capacitor is in series withsecondary windings of the transformer; and generating a RF output signalbased on a RF signal received from the RF generator and in accordancewith the changed capacitance of the first and second capacitors in theimpedance match module, wherein a second reflected power level at a timeafter the first reflected power level is less than the first reflectedpower level.

In some embodiments, an apparatus includes a control module; anoscillator module that is to convert a direct current (DC) signal into aradio frequency (RF) signal; a power amplifier module coupled to anoutput of the oscillator module, the power amplifier module is toamplify a power associated with the RF signal in accordance with a biassignal from the control module to generate an amplified RF signal; and adirectional coupler module coupled to an output of the power amplifiermodule, the directional couple module is to detect at least a reflectedpower and to provide the detected reflected power to the control module,wherein the control module is to generate the bias signal based on thedetected reflected power and is to provide the detected reflected poweras an available monitored output of the apparatus.

In some embodiments, a method includes converting a direct current (DC)signal into a radio frequency (RF) signal; amplifying a power associatedwith the RF signal in accordance with a bias signal from a controlmodule to generate an amplified RF signal; detecting at least areflected power and providing the detected reflected power to thecontrol module; and generating the bias signal based on the detectedreflected power and providing the detected reflected power as anavailable monitored output.

In some embodiments, an apparatus includes means for converting a directcurrent (DC) signal into a radio frequency (RF) signal; means foramplifying a power associated with the RF signal in accordance with abias signal from a means for controlling to generate an amplified RFsignal; means for detecting at least a reflected power and providing thedetected reflected power to the means for controlling; and means forgenerating the bias signal based on the detected reflected power andproviding the detected reflected power as an available monitored output.

In some embodiments, an apparatus includes a radio frequency (RF)generator that is to generate a RF signal; first and second electrodes;and an impedance match module in series between the RF generator and thefirst electrode, wherein the RF generator detects reflected power fromthe RF signal applied to a load electrically coupled between the firstand second electrodes to change a temperature of the load, the RF signalto be applied to the load until the reflected power reaches a particularvalue.

In some embodiments, a method includes applying a radio frequency (RF)signal to a load; monitoring a reflected power level associated with anapparatus including a direct current (DC) source, an impedance matchmodule, a radio frequency (RF) generator, and the load; and determininga temperature of the load based on the reflected power level.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thepresent disclosure will become more readily appreciated as the samebecome better understood by reference to the following detaileddescription, when taken in conjunction with the accompanying drawings.

FIG. 1 depicts a block diagram of an example radio frequency (RF)processing system incorporating aspects of the present disclosure,according to some embodiments;

FIG. 2 depicts a cross-sectional view of an example of the RF generator,according to some embodiments;

FIG. 3 depicts a block diagram of an example of the RF generator,according to some embodiments;

FIG. 4 depicts a circuit diagram of an example of the directionalcoupler module 306, according to some embodiments;

FIG. 5 depicts a block diagram of an example of at least a portion ofthe system of FIG. 1, according to some embodiments;

FIG. 6 depicts a circuit diagram of an example of the RFPA module,according to some embodiments;

FIG. 7 depicts a cross-sectional view of an example of the cavity,according to some embodiments;

FIG. 8A depicts a circuit diagram of an example of the impedancematching module, according to some embodiments;

FIG. 8B depicts a circuit diagram showing an example of an equivalentcircuit of the variable inductance associated with the circuit of FIG.8A, according to some embodiments;

FIG. 9 depicts a top view of an example of electronic components whichmay be used to implement the circuit of FIG. 8A, according to someembodiments;

FIGS. 10A-10B depict additional views of an example of the transformer,according to some embodiments;

FIG. 11 depicts an example process that may be performed by the systemof FIG. 1, according to some embodiments;

FIG. 12A depicts a graph showing temperatures of a material of interestover the time period of an example process performed by the system ofFIG. 1, according to some embodiments;

FIG. 12B depicts a graph showing example freeze curves, according tosome embodiments;

FIG. 13 depicts a block diagram of an example RF processing systemincorporating aspects of the present disclosure, according to additionalembodiments;

FIG. 14 depicts a process that may be performed by the system of FIG. 13to thermally process the material of interest, according to someembodiments;

FIG. 15 depicts a process that may be performed by the system of FIG. 13to thermally process the material of interest, according to alternativeembodiments; and

FIG. 16 depicts a process of endpoint detection techniques which may beperformed by the system of FIGS. 1 and/or 13, according to someembodiments.

DETAILED DESCRIPTION

Embodiments of apparatuses and methods related to radio frequency (RF)processing are described. In embodiments, a system includes a pluralityof radio frequency (RF) generators; a plurality of impedance matchmodules; a plurality of electrode plates, first and second impedancematch modules of the plurality of impedance match modules electricallycoupled between respective first and second RF generators of theplurality of RF generators and respective first and second electrodeplates of the plurality of electrode plates; and a conveyor including aground electrode. When a load at a start temperature is to be placed onthe conveyor, the system uses RF signals generated by the plurality ofRF generators to cause the load to be at an end temperature differentfrom the start temperature, wherein the conveyor is to position the loadto electrically couple to the first electrode plate during a first timeperiod and the first impedance match module is associated with a firstrange of temperatures between the start and end temperatures, andwherein the conveyor is to position the load to electrically couple tothe second electrode plate during a second time period and the secondimpedance match module is associated with a second range of temperaturesbetween the start and end temperatures that is different from the firstrange of temperatures. These and other aspects of the present disclosurewill be more fully described below.

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will be describedherein in detail. It should be understood, however, that there is nointent to limit the concepts of the present disclosure to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives consistent with the presentdisclosure and the appended claims.

References in the specification to “one embodiment,” “an embodiment,”“an illustrative embodiment,” etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may or may not necessarily includethat particular feature, structure, or characteristic. Moreover, suchphrases are not necessarily referring to the same embodiment. Further,when a particular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to affect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described. Additionally, it should be appreciated that itemsincluded in a list in the form of “at least one A, B, and C” can mean(A); (B); (C); (A and B); (B and C); (A and C); or (A, B, and C).Similarly, items listed in the form of “at least one of A, B, or C” canmean (A); (B); (C); (A and B); (B and C); (A and C); or (A, B, and C).

The disclosed embodiments may be implemented, in some cases, inhardware, firmware, software, or any combination thereof. The disclosedembodiments may also be implemented as instructions carried by or storedon one or more transitory or non-transitory machine-readable (e.g.,computer-readable) storage medium, which may be read and executed by oneor more processors. A machine-readable storage medium may be embodied asany storage device, mechanism, or other physical structure for storingor transmitting information in a form readable by a machine (e.g., avolatile or non-volatile memory, a media disc, or other media device).

In the drawings, some structural or method features may be shown inspecific arrangements and/or orderings. However, it should beappreciated that such specific arrangements and/or orderings may not berequired. Rather, in some embodiments, such features may be arranged ina different manner and/or order than shown in the illustrative figures.Additionally, the inclusion of a structural or method feature in aparticular figure is not meant to imply that such feature is required inall embodiments and, in some embodiments, it may not be included or maybe combined with other features.

FIG. 1 depicts a block diagram of an example radio frequency (RF)processing system 100 incorporating aspects of the present disclosure,according to some embodiments. As described in detail below, system 100may be configured to uniformly heat a material of interest from a starttemperature to an end temperature. In some embodiments, the starttemperature may comprise a commercial storage temperature of thematerial of interest. For example, the commercial storage temperature(also referred to as a commercial cold storage temperature) may comprisea temperature associated with the material of interest being in a frozenstate such as, but not limited to, at −40 degree Celsius (° C.), −20°C., −10° C., less than −40° C., and/or the like. The end temperature maycomprise a temperature below 0° C., −2° C., −3° C., −2° C.±1° C.,between −4 to −2° C., a temperature below at which the material ofinterest undergoes a phase change from a solid (e.g., frozen) to liquid,a temperature below at which drip loss of the material of interest mayoccur, a temperature higher than the start temperature at which system100 may be configured to end processing of the material of interest,and/or the like. System 100 may also be referred to as a heating system,a melting system, a tempering system, a dielectric heating system,and/or the like.

System 100 may include a direct current (DC) power source 102, a RFgenerator 104, an impedance matching module 106, a stepper motor 108, acavity 110, a switch 112, and a switch 114. The output of the DC powersource 102 may be coupled to the input of the RF generator 104, theoutput of the RF generator 104 may be coupled to the input of theimpedance matching module 106, and the output of the impedance matchingmodule 106 may be coupled to the input of the cavity 110. Stepper motor108 may be coupled to each of the RF generator 104 and the impedancematching module 106. Switch 112 may be disposed between RF generator 104and cavity 110, and switch 114 may be disposed between DC power source102 and cavity 110.

DC power source 102 may comprise the power source for the system 100. Insome embodiments, DC power source 102 may be operable, withoutlimitation, between 0 to 3000 Watt (W), 0 to 5000 W, or the like. As anexample, DC power source 102 may be configured for operation at 2000 Wand to provide a 42 Volt (V) DC input signal to the RF generator 104.

RF generator 104 may be configured to convert the DC signal receivedfrom the DC power source 102 into an alternating current (AC) signalhaving a particular frequency. RF generator 104 may also be configuredto provide one or more control functionalities such as, but not limitedto, thermal shutdown protection, voltage standing wave ratio (VSWR)foldback protection, DC current limiting protection, endpoint detection,and forward and reflected power level detection, to be described indetail below. In some embodiments, RF generator 104 may comprise anair-cooled high-powered RF generator using solid state transistors, suchas laterally diffused metal oxide semiconductor (LDMOS) transistors;have a dynamic power range of 0 to 10 kiloWatt (kW); a frequency rangeof approximately 13 MegaHertz (MHz) to 100 MHz; capable of frequencystability of ±0.005% at least at 27.12 MHz; a harmonic output of atleast −40 dBc (at least 40 decibels lower relative to carrier); anddimensions of approximately 20 centimeter (cm)×13.5 cm×40 cm. Continuingthe example above, RF generator 104 may operate at a forward power ofbetween 0 to 10 kW; have a 50 Ohm (Ω) output impedance; and output an ACsignal at a frequency of 27.12 MHz, 27 MHz, approximately 27 MHz,between 13 to 100 MHz, at a RF frequency that is not a resonantfrequency associated with the cavity 110, or the like.

Impedance matching module 106, also referred to as an impedance matchmodule, may comprise a component configured to match (or nearly match)the output impedance associated with the RF generator 104 to animpedance associated with a load of the system 100. In some embodiments,the load may comprise a combination of the cavity 110 and the materialto be thermally processed (also referred to as the material of interestor load) included in the cavity 110. The impedance associated with theload may be less than or otherwise differ from an output impedanceassociated with the RF generator 104. Each temperature of the load(e.g., the material of interest) may be associated with a particularimpedance value. As the load temperature changes, as would duringprocessing of the material of interest such as heating of the materialof interest, the impedance associated with the load changes over time.Thus, in some embodiments, impedance matching module 106 may beconfigured for dynamic or variable impedance matching capabilities totake into account the changes in load impedance during processing. Theimpedance matching values associated with the impedance matching module106 may be changed or adjusted one or more times in real-time, nearreal-time, and/or continuously during processing of the material ofinterest in the cavity 110, as described in detail below.

Stepper motor 108 may be configured to receive at least an indication ofdetected reflected power values from the RF generator 104, anddynamically control the capacitance values of the impedance matchingmodule 106 in accordance with the indicated reflected power values.Stepper motor 108 may include, without limitation, in addition to one ormore stepper motors, one or more controllers, circuitry, processors, orother logic configured to receive the indication of detected reflectedpower values, determine appropriate change (if any) to the capacitancevalues of the impedance matching module 106 based on the indication ofdetected reflected power values, and actuation of physical change(s) tothe capacitors included in the impedance matching module 106 to affectthe capacitance change. Stepper motor 108 may alternatively comprise avariety of other mechanisms capable of mechanically moving variablecapacitors to change capacitance by a specific amount (e.g., tuningvariable capacitors to a particular capacitance value).

The reflected power may comprise the difference between the forwardpower (outputted by the RF generator 104) and the load power (theportion of the forward power actually delivered to the load). When theimpedance matching module 106 provides a perfect impedance match betweenthe RF generator 104 and the load, the reflected power level may bezero. Conversely, when the there is a mismatch in the impedance matchingprovided by the impedance matching module 106, the reflected power levelmay be greater than zero. Generally, the greater the reflected powerlevel, the greater the amount of impedance mismatch.

Cavity 110 may include, without limitation, at least an electrode, agrounding electrode, and an area between the electrode and groundingelectrode in which material of interest may be located duringprocessing. Cavity 110 may also be referred to as a housing, box,tunnel, load cavity, conveyor belt, belt, or other structure(s) in whichthe material of interest may be located or positioned and which permitsthe material of interest to be selectively electrically coupled to therest of the system 100. As described in detail below, cavity 110 may beconfigured to handle a plurality of sizes of the material of interest.For example, the material of interest may have a height of approximately5 inches, 6 inches, 9 inches, 12 inches, less than 5 inches,approximately 5-12.5 inches, and/or the like. In some embodiments,cavity 110 may include a door, from which the material of interest maybe inserted or removed from the cavity 110.

In some embodiments, switches 112 and 114 may comprise safety featuresincluded in the system 100. When system 100 is in an “on” state and thedoor is in a closed position, switches 112 and 114 may be configured ina closed position and RF energy may accordingly be provided to thecavity. Conversely, when the door included in the cavity 110 isopen—while the system 100 is in the “on” or “off” state—switches 112 and114 may be configured to change to an open position, thereby creatingopen circuit(s) and interrupting or stopping flow of (potential) DCoutput from the DC power source 102 and (potential) RF output from theRF generator 104. Switches 112 and 114 may thus serve as double safetymeasures. Alternatively, one of switches 112 or 114 may be sufficient toprevent inadvertent RF irradiation, such as of personnel in proximity tothe system 100.

In some embodiments, the Q (ratio of the reactance to the resistivecomponent) associated with system 100 may comprise a high value, such as400. The power lost in the impedance match provided by the impedancematching module 106 may be approximately 50 W for the 1250 W RF signal,which comprises a 4% or less than 5% power loss associated with theimpedance match.

In some embodiments, materials which may be processed in the system 100may include, without limitation, one or more of the following: food;biologic material; protein; meats; poultry (e.g., chicken, turkey,quail, duck); beef; pork; red meat; lamb; goat meat; rabbit; seafood;foods encased in one or more bags, plastic, cardboard, can, and/orcontainer (e.g., raw poultry, beef, pork, or seafood products inside avacuum sealed bag and which may, in turn, be packed in cardboard boxes);various cuts of beef (e.g., sirloin, shoulder, trimmings, chuck,brisket, round, ribs, cheek, organs, flank, skirt, bone-in cuts ofbeef); various cuts of pork (e.g., butt, shoulder, loin, ribs, ham,trimmings, cheek, bacon, bone-in cuts of pork); various cuts of poultry(e.g., strips, breasts, wings, legs, thighs, bone-in cuts of poultry);whole or portions of seafood (e.g., fish, salmon, tilapia, tuna, cod,halibut, haddock, octopus, shellfish (with shell on or off), crab,lobster, clams, mussels, crawfish, shrimp (shell on or off));carbohydrates; fruits; vegetables; bakery goods; pastries; dairy;cheese; butter; cream; milks; eggs; juices; broths; liquids; soups;stews; grains; foods that are combinations of one or more of the above(e.g., pizza, lasagna, curry); non-food materials; plastics; polymers;rubbers; metals; ceramics; wood; soil; adhesives; materials having adielectric constant in the range of approximately 1 to 80 (e.g.,dielectric constant of frozen protein at −20° C. may be 1.3, dielectricconstant of frozen protein at −3° C. may be 2 or 2.1, etc.); and/or thelike. Examples of material that may be processed by system 100 include,without limitation, 40 pound block of frozen meat, whole frozen tuna,and the like.

In some embodiments, system 100 may be configured to perform otherprocesses such as, but not limited to, sterilization, pasteurization,curing, drying, heating, and/or the like. For example, system 100 may beconfigured to dry grains, soften butter or cheese blocks, controlmoisture content of baked goods, or heat up food products such as readymeals.

FIG. 2 depicts a cross-sectional view of an example of the RF generator104, according to some embodiments. RF generator 104 may comprise ahousing 200 having a first chamber 202 and a second chamber 204. Firstand second chambers 202, 204 may also be referred to as first and secondcompartments. First chamber 202 may include a plurality of connectors orcouplers configured to be the inputs and outputs of the RF generator104. In some embodiments, the plurality of connectors/couplers maycomprise, without limitation, a DC input connector 206 (to receive theoutput of the DC power source 102), a RF output connector 208 (to outputthe RF signal generated by the RF generator 104), a forward powerconnector 210 (to provide as an output indications of the detectedforward power level), and a reflected power connector 212 (to provide asan output indications of the detected reflected power level). Theplurality of connectors may comprise, for example, coaxial connectors.

First chamber 202 may also include a plurality of printed circuit boards(PCBs) 220-228, in which each PCB of the plurality of PCBs may beconfigured to include a particular circuitry (and/or hardware orfirmware) of the RF generator 104. In some embodiments, the plurality ofPCBs may comprise, without limitation, a control PCB 220, a directionalcoupler PCB 222, a RF power amplifier (RFPA) PCB 224, an oscillator ordriver PCB 226, and a voltage regulator PCB 228. The various circuitsmay be located on different PCBs from each other and the plurality ofPCBs may also be spaced apart from each other within the first chamber202 for electrical isolation. In the presence of high and low powercircuits, having common ground planes among such circuits may be avoidedby placing the circuits on separate PCBs. Alternatively, more than onecircuit may be included in a single PCB. For example, two or more of thecontrol, directional coupler, RFPA, oscillator, and voltage regulatorcircuitry may be provided on a single PCB. More or fewer than five PCBsmay be included in the first chamber 202. The electrical connectionsbetween the plurality of connectors and PCBs are not shown in FIG. 2 forease of illustration.

In some embodiments, first chamber 202 may comprise an air tight orsealed chamber sufficient to protect the electronic components of the RFgenerator 104 (e.g., PCBs 220-228) from debris, dirt, moisture, and/orother contaminants which may otherwise enter and damage such electroniccomponents.

In some embodiments, PCBs 220-228, such as the bottoms of the PCBs220-228, may be in physical contact with a heatsink 230 to facilitateheat dissipation. Heatsink 230 may include a substrate 232 (which mayoptionally include tubing and/or other heat dissipation structures) anda plurality of fins 234. Substrate 232 may comprise copper and theplurality of fins 234 may comprise aluminum. Heatsink 230 may bepartially located in each of the first and second chambers 202, 204. Forinstance, at least a major surface of the substrate 232 may protrudeinto or be co-planar with a side of the first chamber 202, so that thePCBs 220-228 may be in physical contact with the substrate 232, and atleast the plurality of fins 234 may be located within the second chamber204. Heatsink 230 may comprise one or more heatsinks.

In addition to the plurality of fins 234 located in the second chamber204, second chamber 204 may also include one or more fans, such as fans236 and 238, to provide forced air cooling. Alternatively, fans 236 and238 may be optional if sufficient heat dissipation may be achievedwithout active air circulation. In some embodiments, second chamber 204need not be air tight or sealed, and may include a plurality of vents240 at one or more sides (e.g., cutouts in the side(s) of the housing200 coincident with the second chamber 204) to facilitate heatdissipation.

FIG. 3 depicts a block diagram of an example of the RF generator 104,according to some embodiments. RF generator 104 may include, withoutlimitation, a voltage regulator module 300, an oscillator module 302, aRFPA module 304, a directional coupler module 306, and a control module314. In some embodiments, modules 300, 302, 304, 306, 314 may beincluded respectively in PCBs 228, 226, 224, 222, 220.

In some embodiments, the DC signal outputted by the DC power source 102may comprise the input to the voltage regulator module 300. Voltageregulator module 300 may be configured to reduce the received DC signalto a lower voltage signal. For example, if the received DC signalcomprises 40 V, voltage regulator module 300 may reduce such signal to a15 V DC signal. In some embodiments, voltage regulator module 300 maycomprise film resistor voltage regulators. The output of the voltageregulator module 300 may be provided to each of the oscillator module302 and the control module 314.

Oscillator module 302 may be configured to convert the reduced orstepped down DC signal to an AC signal at a particular RF frequency. Theparticular RF frequency may be “fixed” or set in accordance with aparticular crystal included in the oscillator module 302. Oscillatormodule 302 may also be referred to as an exciter, driver, RF exciter, RFoscillator, RF driver, or the like. The RF signal outputted by theoscillator module 302 (RF signal 303) may then be provided to the RFPAmodule 304.

RFPA module 304 may be driven or controlled based on a bias signal 322from the control module 314. In some embodiments, bias signal 322 mayrange between 0 to 4 V. Bias signal 322 may also be provided to theoscillator module 302. RFPA module 304 may be configured to amplify thepower of the received RF signal in an amount in accordance with theamount of applied bias (e.g., the value of the bias signal 322). Theamount of power amplification or gain provided by the RFPA module 302may be a function of the value of the bias signal 322. In someembodiments, RFPA module 302 may include high gain transistors, such asfour LDMOS transistors, configured to amplify the power of the RF signalreceived from the oscillator module 302 by a gain of approximately 28decibel (dB). For instance, the RF signal 303 received from theoscillator module 302 may comprise a signal of approximately 4 to 6 W.Each of the high gain transistors may be configured to use approximately1 to 1.5 W of the RF signal 303 to output about 300 W. Thus, the highgain transistors (and the RFPA module 304 overall) may collectivelyamplify about 4 to 6 W to about 1250 W, less than about 1250 W, higherthan about 1250 W, a range of 0 to 1250 W (depending on the amount ofbias applied to the RFPA module 304), and/or the like. The RF signal 305outputted from the RFPA module 304 to the directional coupler module 306may thus comprise a RF signal having the desired power amplification.

RF signal 305 received by the directional coupler module 306 maycomprise the RF generator output signal 308 (also referred to as the RFoutput or RF out), which may be outputted by the directional couplermodule 306 to the impedance matching module 106. In some embodiments,directional coupler module 306 may be configured to detect the forwardand reflected power levels of the system 100. The RF voltage level orvalue associated with each of the forward and reflected power may bedetected, monitored, or measured continuously, in real-time, or in nearreal-time. The higher the voltage value, the higher the power level.Directional coupler module 306 may be considered to be a power meter ordetector for at least this functionality. The monitored forward andreflected power levels, or indications of the monitored forward andreflected power levels, may be provided by the directional couplermodule 306 to control module 314. For example, signals 310, 312associated with the monitored forward and reflected power levelsprovided to the control module 314 may comprise small voltage signalsthat are proportional to the actual forward and reflective power levelsdetected, respectively. Zero to 2.5 V may represent 0 to approximately90 W, for instance. Other scaling or conversion factors may also beimplemented.

FIG. 4 depicts a circuit diagram of an example of the directionalcoupler module 306, according to some embodiments. Directional couplermodule 306 may comprise a transformer type of directional coupler. Asshown in FIG. 4, the RF signal (labeled RF IN) from the RFPA module 304may be provided to two branches of the circuit—first branch providingthe RF generator output signal 308 and the second branch configured withtwo transformers 400, 402 to monitor the forward and reflected power asdescribed above. A variable trimmer capacitor 404 may be included in thecircuit to improve the accuracy (directivity) of the directional couplermodule 306. Capacitor 404 may be configured to have a capacitancebetween approximately 6 to 50 picoFarad (pF).

In some embodiments, control module 314 may comprise an analog phaselocked loop (PLL) logic circuit using transistor to transistor logicwith no microprocessors. Control module 314 may be configured to receivesignals 310 and 312 and provide as respective output signals 318 and320. At least signal 320 (reflected power level indicator), for example,may be used by the stepper motor 108 to dynamically adjust the impedanceof the impedance matching module 106. As another example, one or both ofthe signals 318, 320 may be provided to another control module,processor, compute device, and/or the like for additional functionality.Signal 316 may comprise a set point input signal to turn “on” the RFgenerator 104. Signal 316 may range between 0 to 10 V.

Control module 314 may be configured to provide power foldbackprotection. In some embodiments, control module 314 may include anoperational amplifier 500 (as depicted in an example block diagram inFIG. 5) configured to continuously compare the forward and reflectedpower levels using received signals 310 and 312. If the reflected powerlevel is above a pre-determined threshold (e.g., reflected power levelis greater than 15% of the forward power level, reflected power levelequals or is greater than a certain voltage), the output of theoperational amplifier 500 outputs a bias signal 322 that may be lowerthan the immediately previous value. With a lower bias applied to theRFPA module 304, the next RF signal 305 generated by the RFPA module 304is of a proportionately lower power. The next forward power is hence“folded back” or lowered relative to the present forward power. The“folding” back of the forward power may be slowly, gradually, orincrementally implemented rather than shutting off one or more modulesand/or the RF generator 104, which may effectively shut off/down system100 overall. Depending on the rate and/or amount of change of the biassignal 322 over time, the foldback may conform to a shape of apre-defined power foldback curve.

In some embodiments, a potentiometer 502 (see FIG. 5) included in thecontrol module 314 may be used to define the pre-determined threshold atwhich foldback may be triggered. For example, potentiometer 502 may beset for the pre-determined threshold to be at when the reflected powerreaches 3 V.

The power foldback protection provided by the control module 314 maycomprise soft power foldback protection, in which the bias applied tothe RPFA module 304 may be reduced one or more times in response to agiven foldback trigger condition but the applied bias may not be reducedto zero or no bias. The power associated with the RF signal 305/308 maybe folded back merely to a safe level rather than shutting off/down allprocessing, which may be the case with a hard power foldback. Forinstance, the power associated with RF signal 305/308 (e.g., the forwardpower) may be 1250 W at a first point in time, then the reflected powerincreases to the level where the pre-determined threshold is met. Inresponse, the control module 314 may start reducing the bias signal 322to the RFPA module 304 one or more times until the reflected power levelno longer satisfies the pre-determined threshold (e.g., by falling belowthe pre-determined threshold). At such time, the power associated withthe RF signal 305/308 may at 900 W, as an example.

This feedback control loop implemented in the control module 314 may beconsidered to be a safety feature that enables protection of transistors(and possibly other components) included in the RF generator 104. Forinstance, when the reflected power level approaches approximately 10 to15% of the forward power level, the amount of power dissipation in thetransistors may double relative to when the reflected power levels arelow. Subjecting transistors (such as the LDMOS transistors included inthe RFPA module 304) to too high power dissipation may result intransistor damage, failure, fire, damage or failure to nearbycomponents, and/or the like. In embodiments where the RFPA module 304may output RF signals greater than 1250 W, such as 2 kiloWatt (kW),power foldback protection may be even more relevant to protectcomponents. Notice that even with the forward power “folded” back,system 100 continues processing the material of interest, albeit at alower power level than previously. Because of the continuous monitoringand adjustment of the bias signal 322, dynamic control of the RF signal308 outputted to the impedance matching module 106 may be achieved.

In some embodiments, control module 314 may be configured to include atemperature based protection feature. When a thermistor (or atemperature sensor) included in the RF generator 104 detects a certaintemperature associated with the RF generator 104, such as of the heatsink 230, the thermistor may be configured to change its value or state.Such change in the thermistor value or state triggers the control module314 to communicate a temperature signal 324 to the RFPA module 304 andto reduce the bias signal 322 to 0 V, thereby turning off the RFPAmodule 304. Thermistor may experience a value or state change when theheat sink 230 gets too hot, one or both of the fans 236, 238 may benon-operational or blocked, or some other internal thermal buildup hasreached too high a level. The thermistor, in some embodiments, maycomprise an inexpensive component that may be mounted to one of thescrews associated with a transistor of the RF generator 104, and whichis configured to decrease in voltage as the temperature increases untilwhen the voltage reaches a pre-set value (such as 1.9 V), the thermistorregisters a state change.

Although not shown in FIG. 3, various electrical connections into andout of one or more of modules 300, 302, 304, 306, 314 may compriseshielded connections (such as shielded using coaxial cables) and whichmay be separately grounded. For example, the electrical connections inwhich bias signal 322, signal 310, signal 312, signal 316, signal 303,signal 305, signal 318, and/or signal 320 may be respectivelytransmitted may comprise shielded connections with a separate ground.Although modules 300, 302, 304, 306, 314 may comprise circuitry, one ormore of the functionalities of modules 300, 302, 304, 306, and/or 314may alternatively be implemented using firmware, software, otherhardware, and/or combinations thereof.

FIG. 6 depicts a circuit diagram of an example of the RFPA module 304,according to some embodiments. The example circuit diagram maycorrespond to system 100 operating at 27.12 MHz and a maximum RF powerof 1250 W or up to 1400 W depending on ambient air temperature. As shownin FIG. 6, the circuit may comprise first and second branches 600, 630at the input side (left side of circuit) which are combined together atthe output side (right side of circuit), to be described below. Thefirst and second branches 600, 630 may be identical to each other. Withthe two branch configuration, the LDMOS transistors (transistors 606,608, 636, 638) included therein may be implemented in a push-pullconfiguration which provides automatic attenuation, cancellation, orelimination of even order harmonics of the fundamental frequency. Thus,no or very low second, fourth, sixth, and up harmonics may be present.

The circuit shown in FIG. 6 may comprise a plurality of stages orportions. With respect to the first branch 600, going from left toright, may include an input stage, an input transformer stage, a LDMOStransistor stage, an output transformer stage, a signal combiner stage612, and an output stage. Similarly, the second branch 630, going fromleft to right, may include an input stage, an input transformer stage, aLDMOS transistor stage, an output transformer stage, the signal combinerstage 612, and an output stage. The signal combiner and output stagesare shared in both the first and second branches 600, 630.

In some embodiments, RF signal 303 outputted from the oscillator module302 may comprise two identically split RF signals 602 and 632. A singleRF signal generated by the oscillator module 302 may be split into twoidentical RF signals using a splitter included in the oscillator module302 just prior to being outputted to the RFPA module 304. Each of thesplit RF signals 602, 632 may have half the power of the single RFsignal. As an example, each of the split RF signals 602, 632 may have apower of 3 W. Split RF signals 602, 632 may be generated to serve as thedriving or input signal for first and second branches 600, 630,respectively. Alternatively, RF signal 303 from the oscillator module302 may comprise a single signal which may be split upon receipt in theRFPA module 304.

The receipt of split RF signal 602 may occur in the input stage of thefirst branch 600. Next, an input transformer 604 (with associatedcircuitry) included in the input transformer stage may be configured toprocess the split RF signal 602 suitable to be inputs for the LDMOStransistor stage. Input transformer 604 may be configured to furthersplit the split RF signal 602 into a pair of signals, each having apower of 1.5 W. Input transformer 604 may comprise a low powertransformer. Input transformer 604 may comprise a variety of types oftransformers, including tube transformers with ferrite toroids.

The signals may next comprise the inputs to a pair of LDMOS transistors606, 608 included in the LDMOS transistor stage of the first branch 600.Each of the LDMOS transistors 606, 608 (with associated circuitry) maybe configured to provide power amplify the input signal on the order ofapproximately 30 dB (e.g., convert a 1.5 W RF signal into a up to 300 WRF signal). LDMOS transistors 606, 608 may comprise electroniccomponents that are inexpensive, reliable, durable, long operationallife, and the like in comparison to vacuum tubes. The outputs of theLDMOS transistors 606, 608, now high power RF signals, may then beinputs to an output transformer 610 included in the output transformerstage. The drains of the LDMOS transistors 606, 608 may be electricallycoupled to primary windings of the output transformer 610. In someembodiments, output transformer 610 may comprise a tube transformer withpowdered iron toroids or non-ferrite based transformer. To avoiddegradation of ferrite material in the presence of high power signals,non-ferrite based transformers may be implemented for the outputtransformer 610. The RF signal at the secondary windings of the outputtransformer 610 is the input to the signal combiner stage 612.

Second branch 630 may similarly process split RF signal 632 using stagesincluding an output transformer 634, LDMOS transistors 636, 638, andoutput transformer 640 as discussed above for output transformer 604,LDMOS transistors 606, 608, and output transformer 610, respectively.

In some embodiments, the signal combiner stage 612 may be configured tocombine two inputs into a single output. The secondary windings of theoutput transformer 610 may be electrically coupled to a (shunt)capacitor C23 having a capacitance of 10 pF, which in turn may beelectrically coupled to an inductor L8 having an inductance of 0.3 μH,which in turn may be electrically coupled to another (shunt) capacitorC25 having a capacitance of 51 pF. Capacitors C23, inductor L8, andcapacitor C25 may comprise one input branch of the signal combiner stage612. The secondary windings of the output transformer 640 may beelectrically coupled to a (shunt) capacitor C24 having a capacitance of10 pF, which in turn may be electrically coupled to an inductor L9having an inductance of 0.3 μH, which in turn may be electricallycoupled to another (shunt) capacitor C26 having a capacitance of 51 pF.Capacitors C24, inductor L9, and capacitor C26 may comprise anotherinput branch of the signal combiner stage 612. A (shunt) capacitor C27having a capacitance of 120 pF may be common to both input branches andcomprise the output branch of the signal combiner stage 612.

The signal combiner configuration shown in FIG. 6 may comprise anon-conventional Wilkinson combiner configuration. In a conventionalWilkinson combiner, the impedance associated with each of the two inputbranches is half the impedance associated with the output branch. Thereactance that may be required to match two input impedances of 25 Ohm(Ω) to a single 50Ω output impedance is 70Ω for each component. In FIG.6, the input impedance is not 25Ω, deviating from conventional Wikinsoncombiners. Instead, in FIG. 6, the reactance associated with inductor L8may be 50Ω (+j50), the reactance associated with capacitors C23 pluscapacitor C25 may be 100Ω (−j100), and reactance associated withinductor L8 (at 0.3 μH) and capacitor C24 plus capacitor C26 may be 100Ω(−j100). In FIG. 6, inductors L5 and L6 may comprise RF chokes and eachmay be 0.2 μH, and inductors L1-L4 may be 0.1 μH.

The parameter values of at least components included in the signalcombiner stage 612 may be selected to facilitate signal waveform shapingand/or Class E operation/generation. The voltage waveform shape at thedrains of the LDMOS transistors 606, 608, 638, 640 may have a square (orapproximately a square) waveform shape. Class E operation refers to thehighest class of power efficiency operation. RF signal 305 may comprisea signal having a 75 to 80% power efficiency in DC to RF conversion,having a DC to RF conversion efficiency greater than 50%, or the like.

FIG. 7 depicts a cross-sectional view of an example of the cavity 110,according to some embodiments. Cavity 110 may include, withoutlimitation, a housing 700, a first electrode plate 702, a secondelectrode plate 704, and a RF signal conduit or cable 706. Housing 700may include an opening through which the RF signal conduit or cable 706may pass through. One end of the RF signal conduit or cable 706 may beelectrically coupled to the output of the impedance matching module 106.The opposite end of the RF signal conduit or cable 706 may electricallycouple to first electrode plate 702. RF signal generated by the RFgenerator 104 (e.g., 27.12 MHz, 1250 W signal) may be transmittedthrough the RF signal conduit or cable 706 to a material of interest 708located between the first and second electrode plates 702, 704.

The first electrode plate 702, also referred to as an electrode or topelectrode, may be fixedly positioned at a particular location betweenthe top and bottom of the housing 700. A distance or height 710 mayseparate the top of the housing 700 from the first electrode plate 702,and a distance or height 716 may separate the first electrode plate 702from the bottom of the housing 700. Second electrode plate 704, alsoreferred to as an electrode, bottom electrode, or ground electrode, maycomprise the bottom (or at least a portion of the bottom) of housing700. Second electrode plate 704 may comprise a grounding plane of thecavity 110. Alternatively, second electrode plate 704 may comprise anelectrode plate located above the bottom of housing 700 and grounded toa ground plane of the housing 700.

Each of the housing 700, first electrode plate 702, and second electrodeplate 704 may comprise a conductive material, a metal, a metal alloy,stainless steel, aluminum, and/or the like. RF signal conduit or cable706 may comprise a coaxial cable.

In some embodiments, the length and width of each of the first andsecond electrode plates 702, 704 may be the same or approximately thesame as the length and width of the material of interest 708.Alternatively, the length and/or width of the first and/or secondelectrode plates 702, 704 may be different (e.g., larger) than that ofthe material of interest 708. The length and width of at least the firstelectrode plate 702 may be smaller than the interior length and width ofhousing 700 so that first electrode plate 702 does not physicallycontact the sides of the housing 700. For instance, a gap of half aninch may exist between the first electrode plate 702 on all sides of thehousing 700.

When material of interest 708 is placed inside the housing 700, materialof interest 708 may or may not be in physical contact with one or bothof first and second electrode plates 702, 704. In some embodiments, adistance or gap 712 between the first electrode plate 702 and the top ofthe material of interest 708 may be approximately 0.5 to 1 inches orless, and a distance or gap 714 between the bottom of the material ofinterest 708 and the second electrode plate 704 may be approximately 0.5inches or less. In some embodiments, material of interest 708 may have aheight of approximately 5 inches and accordingly, distance 716 betweenfirst and second electrode plates 702, 704 may be approximately 6inches. The corresponding housing 700 dimensions may then beapproximately 560 millimeter (mm)×430 mm×610 mm. Alternatively, distance716 may be smaller or larger than 6 inches, as discussed in detailbelow. Distance 710 (also referred to as a gap) may be selected toreduce changes in total load impedance with changes in dimensions of thematerial of interest and dielectric constant. The distance 710 maycreate a swamping capacitor to swamp out changes in capacitance 722.This is due to capacitance 720 (C1) being much larger than capacitance722 (C2). The increase in total capacitance reduces the load Q (in whichQ=reactance/resistance). Lowering the reactance of the load impedance,and thus lowering the Q, facilitate tuning the match impedance. Distance710 may be 0.5 to 2 inches or less.

A capacitance 720 (also referred to as capacitance C1) may be defined bythe top of housing 700 and first electrode plate 702 (e.g., pair ofelectrodes), the distance 710 between them, and the dielectricproperties of the material between the pair of electrodes (e.g., air).Since capacitance is inversely proportional to the distance between theelectrodes, as distance 710 decreases, the higher the value ofcapacitance 720. In some embodiments, the smaller the distance 710, thegreater the design flexibility for one or more of the other parameters,dimensions, or the like in system 100. A capacitance 722 (also referredto as capacitance C2) may be defined by the first and second electrodeplates 702, 704 (e.g., pair of electrodes), the distance 716 betweenthem, and the dielectric properties of the material between the pair ofelectrodes (e.g., a combination of air and material of interest 708(e.g., meat, ice, and salt)). Capacitance 720 is arranged in parallelwith capacitance 722.

FIG. 8A depicts a circuit diagram of an example of the impedancematching module 106, according to some embodiments. Impedance matchingcircuit 800, also referred to as an LL match circuit, may be configuredto include a capacitor 804 (also referred to as C1), an inductor 806(also referred to as L1), a transformer 808 (also referred to as T1),and a capacitor 810 (also referred to as C2). RF signal 308 outputted byRF generator 104 may comprise the input to circuit 800 at capacitor 804.RF signal 802 outputted by circuit 800 at secondary windings oftransformer 808 may be the input to RF signal conduit or cable 706 ofcavity 110 (e.g., to the load).

In some embodiments, capacitor 804 and inductor 806 may be arranged inparallel with each other, and such parallel arrangement, in turn, may bein series with the primary windings of transformer 808 which may formwhat may be referred to overall as a primary circuit. Capacitor 810 andthe secondary windings of transformer 808 may form another seriescircuit, which may also be referred to as a secondary circuit. As thecapacitance of capacitor 804 is changed, the overall reactanceassociated with the primary circuit changes. Due to coupling between thesecondary and primary windings of transformer 808, such change in thesecondary circuit causes a change in the inductance associated with theprimary circuit. Secondary windings of transformer 808 may be consideredto change or control the inductance associated with the primary windingsof transformer 808. The primary circuit, and the primary windings oftransformer 808 in particular, may thus be considered to have variableinductance capabilities.

Capacitor 804 (C1) and capacitor 810 (C2) correspond to respectivecomplex impedance of capacitance 720 (C1) and capacitance 722 (C2)associated with cavity 110. In some embodiments, since capacitance 722(C2) is associated with the material of interest 708 and the material ofinterest 708 is the item undergoing thermal change, capacitance 722 (C2)changes over the course of processing time as the material of interest708 undergoes thermal change. As capacitance 722 (C2) changes over time,so does its associated impedance. In order for the impedance matchingmodule 106 to maintain an impedance match between the RF generator 104and cavity 110, as the impedance associated with the cavity 110 changesover the course of processing due to at least impedance changesassociated with the material of interest 708, capacitance values ofcapacitor 810 (C2) and/or capacitor 804 (C1) in the impedance matchingmodule 106 may be selectively and/or dynamically adjusted accordingly.Capacitors 804, 810 may also referred to as variable value capacitors orvariable capacitance value capacitors.

For example, when the material of interest 708 comprises protein ofapproximately 5 inches in height, distance 716 between first and secondelectrode plates 702, 704 of cavity 110 is approximately 6 inches, andthe material of interest 708 is to be heated from a start temperature ofapproximately −20° C. to an end temperature of −3° C.±1° C., capacitor804 may range between 16 to 107 pF, 16 to 250 pF, or the like; capacitor810 may range between 16 to 40 pF, 16 to 80 pF, or the like; andinductor 806 may be approximately 74 nanoHenry (nH).

The impedance values associated with circuit 800 overall (also referredto as the match impedance values) for different combinations of minimumand maximum capacitance values of capacitors 804, 810 are providedbelow.

Capacitor 804 (C1) Capacitor 810 (C2) Match impedance  20 pF  20 pF 2.0Ω-j50 120 pF  20 pF 3.0 Ω-j55 120 pF 120 pF 3.5 Ω-j72  20 pF 120 pF 3.0Ω-j69 120 pF + a 120 pF capacitor 120 pF 5.0 Ω-j77 added in parallelwith capacitor 804

As can be seen, the real component of the match impedance ranges between2 to 5Ω and the reactive component of the match impedance ranges between−j50 to −j77. Such range in the match impedance provides sufficientmargin to cover possible values of the load impedance (e.g., theimpedance associated with the cavity 110 overall) throughout theprocess. In some embodiments, approximately the center of the matchimpedance range possible based on the range of capacitors 804, 810 maybe selected to be the same as the load impedance values, and theremaining portions of the match impedance range may be selected toprovide a margin of error. For instance, load impedance associated withlean beef at −3° C. may be 3Ω −j60, which is well within (and is nearthe center of) the match impedance range of 2 to 5Ω in real componentand −j50 to −j77 in reactive component.

FIG. 8B depicts a circuit diagram showing an example of an equivalentcircuit of the variable inductance discussed above, according to someembodiments. Also referred to as an LL equivalent circuit, the circuitmay comprise an inductor 820, ranging between 0.28 to 0.44 microHenry(μH), in series with an inductor 822, ranging between 54 to 74 nH, forthe same processing parameters as discussed immediately above.

FIG. 9 depicts a top view of an example of electronic components whichmay be used to implement circuit 800, according to some embodiments.Capacitors 804, 810 may comprise multi-plate or multiple plate type ofcapacitors, in which one or more plates may be mechanically moved to oneor more positions to vary the capacitance. Inductor 806 may comprise astrap inductor. In some embodiments, inductor 806 may comprise a flatstrip of silver plated copper. The inductance value of the inductor 806may be set based on the dimensions of the flat strip of silver platedcopper, in particular the length. For instance, an inductance of 74 nHmay be achieved using a flat strip of silver plated copper havingdimensions of 0.06 inch×0.375 inch×6.0 inch. Alternatively, inductor 806may comprise other types of metals, alloys, or conductive material.

Transformer 808 may comprise an air core type of transformer.Transformer 808 may also be referred to as a flat wound variableinductance transformer. FIGS. 10A-10B depict additional views of anexample of the transformer 808, according to some embodiments. As shownin a cross-sectional view in FIG. 10A, transformer 808 may include atube 1000, a primary coil 1002, and a secondary coil 1004.

Tube 1000 may comprise a hollow cylinder having particular outer andinner diameters and length. In some embodiments, tube 1000 may comprisea non-magnetic, non-conductive, and/or insulative material such as, butnot limited to, Teflon or other material. The dimensions and shape ofthe tube 1000 provide a coefficient of coupling of 0.76. That is, thevoltage induced in the secondary windings may be 0.76 times the voltagein the primary windings. Tube 1000 may also be referred to as a hollowcylindrical form or Teflon tube. Primary coil 1002 may comprise a flatconductive strip, comprising silver plated copper, that is wound orwrapped around the outer surface of the tube 1000. Secondary coil 1004may also comprise a flat conductive strip of silver plated copper(similar material to primary coil 1002) that is wound or wrapped aroundthe inner surface of the tube 1000. Each of the primary and secondarycoils 1002, 1004 may be spirally wrapped around the tube 1000 so that itextends the entire length of tube 1000. As shown in FIG. 10B, one end ofeach of the primary and secondary coils 1002, 1004 may be located at oneend of the tube 1000 and the other end of each of the primary andsecondary coils 1002, 1004 may be located at the opposite end of thetube 1000.

In some embodiments, tube 1000 may have an inner diameter ofapproximately 1.25 inch, an outer diameter of approximately 1.5 inch,and a length of 2.2 inch. Primary coil 1002 may be 0.06 inch thick,0.375 inch wide, and 15.5 inches in length. When wrapped around the tube1000, the wrapped-around diameter of primary coil 1002 may be similar tothat of the outer diameter of tube 1000. Secondary coil 1004 may be 0.06inch thick, 0.375 inch wide, and 15.5 inches in length. When wrappedaround the tube 1000, the wrapped-around diameter of secondary coil 1004may be similar to that of the inner diameter of tube 1000.

Primary and secondary coils 1002, 1004 may also be referred to aswindings, flat strips, thin strips, flat windings, or the like. Inalternative embodiments, primary and secondary coils 1002, 1004 maycomprise conductive materials, metals, alloys, or the like other thansilver plated cooper.

Primary and secondary coils 1002, 1004 may comprise respectively theprimary and secondary windings of the transformer 808. In someembodiments, the number of turns or windings of the primary coil 1002around the outside of the tube 1000 may be three turns, while the numberof turns or windings of the secondary coil 1004 around the inside of thetube 1000 may be four turns. While the lengths of the primary andsecondary coils 1002, 1004 may be the same as each other, because theinner circumference of tube 1000 has a smaller diameter than the outercircumference of tube 1000, the number of turns around the innercircumference is larger than the number of turns around the outercircumference. The inductance associated with each of the primary andsecondary coils 1002, 1004 may be identical to each other. For example,the inductance associated with each of the primary and secondary coils1002, 1004 may be approximately 0.26-0.28 μH.

In alternative embodiments, transformer 808 may be configured to includean additional turn or winding of each of the primary and secondary coils1002, 1004 relative to the number of turns discussed above (for a totalof four turns for primary coil 1002 and five turns for secondary coil1004). Tube 1000 may have the following dimensions: an inner diameter of1.2 inch, an outer diameter of 1.55 inch, and a length of 3 inch. Suchconfiguration may increase the inductance associated with each of theprimary and secondary coils 1002, 1004 by approximately 50 nH from theinductances associated with the transformer configuration discussedabove (e.g., to now approximately 0.31 μH). This transformer may belarger than the version of transformer 808 discussed above, and mayfacilitate providing impedance matching of cavity 110 configured withelectrode distance 716 in the range of approximately 4.5 inches up to12.5 inches. For this configuration, the capacitance values of thecapacitor 810 (C2) may also be reduced relative to the values discussedabove. For example, capacitor 810 (C2) may have a capacitance range ofapproximately 16-80 pF. Impedance matching module 106 may furtherinclude a 1:1 gear pulley mechanism configured to move the plates/finsof the capacitors 804, 810 together. The gear pulley mechanism may beactuated by a single stepper motor.

FIG. 11 depicts an example process 1100 that may be performed by thesystem 100 to thermally process the material of interest 708 to the endtemperature, according to some embodiments. At block 1102, RF generator104 may be configured to receive the DC signal generated by the DC powersource 102. Using the received DC signal and in accordance with the biaslevel applied to the RFPA module 304 by the control module 314, RFgenerator 104 may be configured to generate a RF output signal (e.g., RFoutput signal 308) in accordance with the applied bias, at block 1104.

Simultaneously, at block 1106, directional coupler module 306 includedin the RF generator 104 may be configured to monitor or detect forwardand reflected power levels of the system 100. Block 1106 may beperformed continuously in some embodiments. Alternatively, block 1106may be performed periodically, randomly, at pre-determined times, and/orat some other time basis. The monitored forward and reflected powerlevels (e.g., signals 310, 312) may be provided to the control module314, and the control module 314, in turn, may provide output signals 318and 320. Signals 318, 320 may also be referred to as monitored outputsthat may be available for use by other components. In some embodiments,stepper motor 108 may be coupled to at least the connector associatedwith signal 320—the monitored reflected power level indication signal.Thus, at block 1130, the reflected power level monitored at block 1106may be received by the stepper motor 108 at block 1130.

Returning to block 1106, with knowledge of the current forward andreflected power levels, control module 314 included in the RF generator104 may be configured to determine whether the reflected power levelexceeds a threshold, at a block 1108. If the threshold is not exceeded(e.g., the reflected power level is within acceptable limits) (no branchof block 1108), then the current bias level of bias signal 322 to theRFPA module 304 may be maintained and unchanged, at block 1110. Process1100 may then return to block 1104.

Otherwise, the threshold is exceeded (yes branch of block 1108), and thebias level of bias signal 322 may be reduced by the control module 314,at block 1112. In some embodiments, the reduction of the bias level maybe by a pre-set amount, an amount in proportion to the amount ofexcessive level of the reflected power level, an amount in accordancewith a pre-determined foldback curve, and/or the like. Process 1100 maythen return to block 1104.

Upon receipt of the monitored reflected power level at block 1130, acontrol chip, control logic, controller, or the like included in steppermotor 108 may be configured to determine whether the monitored reflectedpower level exceeds a pre-determined threshold, at block 1132. If thethreshold is not exceeded (no branch of block 1132), the process 1100may return to block 1132 to continue detection of a too high reflectedpower level in the continuous stream of monitored reflected power levelsreceived at block 1130. If the threshold is exceeded (yes branch ofblock 1132), then process 1100 may proceed to block 1134 in whichchanging one or both of capacitors' 804, 810 capacitance values may beinitiated.

In some embodiments, the reflected power level may increase as theamount of mismatch between the match impedance value associated with theimpedance matching module 106 and the load impedance value associatedwith the cavity 110 and the material of interest 708 contained thereinincreases. When the match and load impedances are perfectly matched, thereflected power level may be at zero. Hence, the reflected power levelmay be used to determine the presence of an impedance mismatch, theextent of the impedance mismatch, and/or serve as a trigger to tune (orre-tune) one or both of the capacitors 804, 810 in the impedancematching module 106. As an example, the threshold at which the reflectedpower level may be deemed to be too high may be at 2.0 V. Reflectedpower levels greater than 2.0 V may cause actuation of the steppermotor. The threshold associated with block 1132 may be smaller than thethreshold associated with foldback protection at block 1108 by at leasta 0.5 V amount. The reflected power levels at which foldback may bewarranted tend to be significantly higher than the levels of thereflected power indicative of an impedance mismatch sufficient totrigger a change in the match impedance.

At block 1134, the control chip, control logic, controller, or the likeincluded in stepper motor 108 may be configured to actuate the steppermotor by generating and providing an appropriate adjustment signal tothe mechanism configured to mechanically move/adjust the plate(s) of oneor both of the capacitors 804, 810.

At the impedance matching module 106, when no adjustment signal mayexist (no branch of block 1136), then the capacitance values remainunchanged and process 1100 may proceed to block 1114. Conversely, whenan adjustment signal is generated by the stepper motor 108 (yes branchof block 1136), then one or both of the capacitors 804, 810 may undergomechanical movement or change in configuration to change/adjust/tune thecapacitance in accordance with the adjustment signal, at block 1138. Insome embodiments, capacitors 804, 810 may be initially configured to beat the highest value within its respective capacitance ranges. Asprocessing commences, the stepper motor 108 may be configured tomechanically move or adjust the capacitors 804, 810 by a pre-setincrement amount or “step” down an area associated with the electrodesso that the associated capacitance values decrease. Stepper motor 108may have, for example, one hundred steps or incrementalmovement/adjustment capabilities, which may correspond to the fullcapacitance ranges associated with capacitors 804, 810 (e.g., 16 to 107pF). An adjustment signal may direct the stepper motor to move by onestep or increment, which may correspond to a small change in thecapacitance such as approximately 3 to 5 pF. With the capacitance nowchanged by approximately 3 to 5 pF, the reflected power level inresponse to such change may be detected in block 1132 (in the next roundof reflected power level detection). In some embodiments, stepper motor108 may comprise more than one stepper motor and/or have the capabilityto adjust capacitors 804, 810 independent of each other.

If the reflected power level still exceeds the threshold (yes branch ofblock 1132), then another adjustment signal may be generated in block1134 to mechanically adjust capacitors 804, 810 by one step or incrementand the capacitance value again changes by approximately 3 to 5 pF. Thisloop may be repeated as necessary until the reflected power level isbelow the threshold. If the reflected power level once again exceeds thethreshold, then single step incremental adjustments to the capacitancemay once again occur. Over the course of thermally processing thematerial of interest 708 to the end temperature, capacitors 804 and/or810 may move through their full capacitance range, from their highest tolowest capacitance values.

In some embodiments, one or both of the capacitors 804, 810 may beadjusted in response to an adjustment signal, adjustment of capacitors804, 810 may alternate in response to successive adjustment signals, orthe like. For example, capacitors 804 and 810 may both move or beadjusted per stepper motor actuation.

Alternatively, block 1132 may comprise detection of an increase in thereflected power level relative to the immediately preceding detectedreflected power level or a certain number of the previously detectedreflected power levels. Similar to the discussion above, if an increaseis detected, then process 1100 may proceed to block 1134 to cause a stepup in capacitance in the impedance matching module 106.

With the capacitance tuned (or more closely tune) to provide a matchingimpedance, the RF signal 308 generated by the RF generator 104 in block1104 may be received by the impedance matching module 106 in block 1114.Next at block 1116, the received RF signal 308 may propagate through orbe processed by the current configuration of the impedance matchingmodule 106 (including any capacitor(s) which may have been tuned inblock 1138). The resulting RF signal 802 generated by the impedancematching module 106 may be provided to the cavity 110 at block 1118.

Upon receipt of the RF signal 802 by the cavity 110, at block 1120, thecavity may be configured to apply the received RF signal 802 to thematerial of interest 708, at block 1122.

Because system 100 may be configured to continuously monitor the forwardand reflected power levels (at block 1106), it may be considered thatapplication of a RF signal to the material of interest at a given pointin time may result in the next reflected power being generated, whichmay be detected in block 1106. This feedback loop may be denoted by thedotted line from block 1122 to block 1106.

In some embodiments, at the end of such continuous processing of thematerial of interest 708, the temperature uniformity throughout thematerial of interest's volume may be within ±1.4° C., within 1° C.,within less than 1.5° C., or the like. Such temperature uniformity mayalso exist in the material of interest 708 during the course of theprocess.

FIG. 12A depicts a graph 1200 showing temperatures of the material ofinterest 708 over the time period of an example process performed by thesystem 100, according to some embodiments. A line 1202 shows thetemperatures of the material of interest 708 from a start temperature of−20° C. at a start time to an end temperature of −4° C. at about 35 to40 minutes as RF energy is continuously applied to the material ofinterest 708 throughout the 40 minute time period. Notice that the timeassociated with raising the temperature of the material of interest 708from −10° C. to −4° C. (the latter part of the temperature range) ismore than the time associated with the raising the temperature in theinitial part of the process.

Time period for processing a material of interest from less than −20° C.(such as −40° C.) to −3° C.±1° C. may be approximately 40 to 50 minutesor less than an hour. Because the temperature change is rapid attemperatures well below about −10° C., a start temperature less than−20° C. does not add much to the overall processing time then for astart temperature at −20° C.

FIG. 12B depicts a graph 1210 showing example curves 1212 and 1214,according to some embodiments. Curve 1212 may be associated with air,while curves 1214 may be associated with various materials. Althoughcurves 1212 and 1214 may be associated with freezing materials or air,materials in the presence of uniform heat flux (e.g., materials arebeing heated) may exhibit similar temperature change profiles, except inreverse as a function of time. As shown by section 1216 of the curves1214, materials may exhibit nearly linear change in temperature asfunction of time when heating from approximately −20° F. to about 27° F.Materials may also exhibit a time period during which they may notchange temperatures even though energy is being applied or extracted, asshown in a horizontal (or nearly horizontal) section 1218 of curves1214. This section may be referred to as the latent zone. The lack oftemperature change in section 1218 may be associated with the materialsundergoing phase change from a liquid to solid (e.g., water in thematerials turning to ice).

FIG. 13 depicts a block diagram of an example RF processing system 1300incorporating aspects of the present disclosure, according to additionalembodiments. System 100 may comprise a stationary RF processing system,in that the material of interest (e.g., the load) does not move withinthe system 100 during the applied process, while system 1300 maycomprise a RF processing system in which the material of interest movesand/or is repositioned at one or more areas within the system 1300during the process, as described in detail below.

In some embodiments, system 1300 may include, without limitation, atunnel 1302, a conveyor 1304, a ground electrode plate 1306, an infeeddoor 1308, an outfeed door 1310, a plurality of processing cells 1312, amaster control module 1350, a compute device 1352, and a compute device1356. Tunnel 1302 and the compartment(s)/chamber(s) including theplurality of processing cells 1312 are shown in cross-sectional view inFIG. 13.

Tunnel 1302 in combination with the infeed and outfeed doors 1308, 1310may comprise an enclosure in which the material of interest 708 may bethermally processed. Tunnel 1302 may have a variety of shapes such as,but not limited to, a square tube, a rectangular tube, or the like.Tunnel 1302 may also be referred to as cavity, housing, enclosure, orthe like. Tunnel 1302 may be analogous to the cavity 110 for the system1300.

The bottom of the tunnel 1302 may include a conveyor 1304 that extendsat least the length of the tunnel 1302 or extends the length of thetunnel 1302 and also further out than the tunnel 1302 on one or bothends of the tunnel 1302. Conveyor 1304 may include belts, rollers, orother transport mechanisms to cause items placed thereon (e.g., materialof interest 708) to move or be transported in a direction 1305. Themovement in the direction 1305 may be continuous, intermittent, atconstant speed, at variable speed, indexed, on command, and/or the like.Disposed above the conveyer 1304 may be the ground electrode plate 1306.Ground electrode plate 1306 may comprise a conductive material that iselectrically grounded. Ground electrode plate 1306 may also be referredto as a ground plate, a ground electrode, or the like. Tunnel 1302 mayinclude the infeed door 1308 at one opening/end and the outfeed door1310 at the opposite opening/end. Infeed door 1308 may comprise a dooror opening through which the material of interest 708 may enter thetunnel 1302. Outfeed door 1310 may comprise a door or opening throughwhich the material of interest 708 may exit the tunnel 1302. Inalternative embodiments, one or both of doors 1308, 1310 may be omittedin system 1300.

In some embodiments, the plurality of processing cells 1312 may belocated above the tunnel 1302. The plurality of processing cells 1312(with the exception of the electrode plates 1326, 1336, 1346) may belocated in a different chamber or compartment from the tunnel 1302. Oneor more of the processing cells of the plurality of processing cells1312 may be located in a different chamber or component from each other.

The plurality of processing cells 1312 may comprise N cells, in whicheach ith cell of the plurality of processing cells 1312 may include a DCpower source, a RF generator, an impedance matching module, a steppermotor, and an electrode plate. The DC power source may be similar to DCpower source 102, RF generator may be similar to RF generator 104,impedance matching module may be similar to impedance matching module106, stepper motor may be similar to stepper motor 108, and theelectrode plate may be similar to electrode plate 702.

For instance, as shown in FIG. 13, cell 1 may include a DC power source1320, a RF generator 1322, an impedance matching module 1324, a steppermotor 1326, and an electrode plate 1326. The RF generator 1322 may beelectrically coupled between the DC power source 1320 and impedancematching module 1324, the output of the impedance matching module 1324may be electrically coupled to the electrode plate 1326, and the steppermotor 1326 may be electrically coupled to the impedance matching module1324. Cell 2 may include a DC power source 1330, a RF generator 1332, animpedance matching module 1334, a stepper motor 1336, and an electrodeplate 1336. The RF generator 1332 may be electrically coupled betweenthe DC power source 1330 and impedance matching module 1334, the outputof the impedance matching module 1334 may be electrically coupled to theelectrode plate 1336, and the stepper motor 1336 may be electricallycoupled to the impedance matching module 1334. Cell N may include a DCpower source 1340, a RF generator 1342, an impedance matching module1344, a stepper motor 1346, and an electrode plate 1346. The RFgenerator 1342 may be electrically coupled between the DC power source1340 and impedance matching module 1344, the output of the impedancematching module 1344 may be electrically coupled to the electrode plate1346, and the stepper motor 1346 may be electrically coupled to theimpedance matching module 1344.

In some embodiments, a physical separation or gap may exist betweenadjacent cells, or between at least the electrode plates 1326, 1336,1346, of the plurality of processing cells 1312 along direction 1305.The physical separation or gap may be at least a couple of inches toensure electrical isolation between adjacent cells. The electrode plates1326, 1336, 1346 may be disposed or positioned a particular distance/gapfrom the top of the tunnel 1302, similar to distance 710 in cavity 110.The particular distance/gap above the electrode plates 1326, 1336, 1346(along with the electrode area and dielectric characteristics betweenthe electrodes) may be associated with a capacitance C1—such ascapacitances 1328 and 1338 for respective electrode plates 1326 and1336—which may be similar to capacitance 720 (C1) in cavity 110.Likewise, electrode plates 1326, 1336, 1346 may be disposed orpositioned a particular distance/gap from the ground electrode plate1306, similar to distance 722 in cavity 110. The particular distance/gapbetween electrode plates 1326, 1336, 1346 and ground electrode plate1306 (along with the electrode area and dielectric characteristicsbetween the electrodes) may be associated with a capacitance C2—such ascapacitances 1329 and 1339 for respective electrode plates 1326 and1336—which may be similar to capacitance 722 (C2) in cavity 110.

In some embodiments, the components included in each processing cell ofthe plurality of processing cells 1312 may be identical to each otherexcept for the capacitance range of the capacitors included in theimpedance matching module in the respective processing cells. Thecapacitors included in the impedance matching modules (e.g., impedancematching modules 1324, 1334, 1344) of the plurality of processing cells1312 may comprise capacitors 804, 810 as shown in FIG. 8A. Thecapacitance range in respective processing cells may differ from eachother.

In some embodiments, each cell of the plurality of processing cells 1312may be associated with a particular range of temperatures between thestart temperature and the end temperature, in which each cell may beassociated with a range of temperatures different from each other. Thecapacitance range in respective processing cells may likewise beselected in accordance with the expected particular temperature range ofthe material of interest 708 at the respective cells. The starttemperature may comprise the temperature of the material of interest 708at which processing at the first cell (cell 1) starts. The starttemperature may also be referred to as the infeed temperature. The endtemperature may comprise the temperature of the material of interest 708after processing at the last cell (cell N) has been completed. The endtemperature may also be referred to as the outfeed temperature.

In contrast to system 100, which processes the material of interest 708at a start temperature to an end temperature using the same DC powersource 102, RF generator 104, impedance matching module 106, steppermotor 108, and electrode plates 702, 704, system 1300 may be configuredto process the material of interest 708 from the start temperature tothe end temperature in stages using the plurality of processing cells1312. The material of interest 708 may successively advance from cell 1to cell N, each ith cell configured to change the temperature of thematerial of interest 708 from an ith start temperature to an ith endtemperature higher than the ith start temperature.

For example, the plurality of processing cells 1312 may comprise eightcells (N=8) and the material of interest 708 is to be processed from astart temperature of −20° C. to an end temperature of −2° C. The rangeof temperatures associated with each cell may be approximately thedifference between the start and end temperatures divided by the numberof cells. For eight cells, each cell may be configured to process atemperature range of approximately 2.25° C. (=18° C./8). Cell 1 may beconfigured to process the material of interest 708 from −20° C. to−17.75° C., cell 2 may be configured to process the material of interest708 from −17.75° C. to 15.5° C., and so forth to cell N which may beconfigured to process the material of interest 708 from −4.25° C. to −2°C. In some embodiments, the temperature range of respective cells may ormay not be identical to each other. Certain one or more of the cells maybe associated with a wider or narrower temperature range than theremaining cells. For instance, cell 1 and cell N may be configured tohandle a 3 or 4° C. temperature range while the remaining cells may beconfigured for a less than 2° C. temperature range. It is understoodthat although eight cells are discussed above, the number of cells maybe less or greater than eight cells such as, but not limited to, two,four, five, six, 10, 12 cells or the like.

In some embodiments, the capacitance range associated with the impedancematching module of each cell may be a sub-range of values of the fullcapacitance range if the material of interest 708 was processed in astationary system such as system 100. The sub-range of values of thefull capacitance range associated with each cell may be different fromeach other. The capacitors in the impedance matching module (e.g.,capacitors 804, 810 as in FIG. 8A) of each cell may be tunable betweenthe lowest to highest value of its associated assigned sub-range ofvalues. When the capacitors have tuned through the sub-range but themeasured reflected power level for the cell is still above a threshold,then the material of interest may be at a temperature outside thetemperature range assigned for that cell and the material of interest isto be advanced to the next cell, as described in detail below.

In alternative embodiments, the capacitors included in the impedancematching modules may comprise fixed value capacitors (also referred toas fixed capacitance value capacitors) that do not change duringprocessing of the material of interest. Stepper motors (e.g., steppermotors 1326, 1336, 1346) may be optional in system 1300 if fixedcapacitance is implemented in the cells. Each of the impedance matchingmodules 1324, 1334, 1346 may include the circuit 800 except capacitors804 (C1) and 810 (C2) may either be set to particular values or may bereplaced with fixed capacitors at the particular values. An example offixed capacitance values of C1 and C2 in the impedance matching modulesin a eight cell configuration, for a −20° C. to −2.5° C. process, withan approximately 6 inch distance between electrode plates 1326, 1336,1346 and ground electrode plate 1306, and in which the material ofinterest 708 may comprise protein is provided below.

Processing Incoming time at Match Temperature cell RF power impedance C1C2 Cell (° C.) (minutes) (W) (ohm) (pF) (pF) 1 −20.0 5 1000 2.50-j63.0 100 60 2 −17.5 5 1000 2.57-j62.57 90 57 3 −15.0 5 1000 2.64-j62.14 80 544 −12.5 5 1000 2.71-j61.71 70 51 5 −10.0 5 1100 2.78-j60.28 60 48 6 −7.55 1200 2.85-j60.85 50 45 7 −5.0 5 1300 2.92-j60.42 40 42 8 −2.5 5 13002.99-j59.99 30 39In the table above, an example of RF power which may be increased in thelater cells relative to the starting cells is also shown. Such powerincrease may be implemented to speed up the processing time in thosecells.

In still other embodiments, the plurality of processing cells 1312 maybe implemented using a mix of variable capacitor cells and fixedcapacitor cells. The fewer the number of cells comprising the pluralityof processing cells 1312, the greater the number of cells may beconfigured with variable capacitors. The fewer the number of cellscomprising the plurality of processing cells 1312, the more likely thecells may be configured as variable capacitor cells in order to maintainimpedance match in each cell.

In some embodiments, total time to bring the material of interest 708 tothe final end temperature (e.g., −2° C.±1° C.) may be approximately thesame in both systems 100 and 1300. In system 1300, the amount of timethat the material of interest 708 may spend electrically coupled to aparticular cell may be approximately the total processing time dividedby the number of cells. For example, for start and end temperatures of−20° C. and −2° C., respectively, the amount of processing time at agiven cell may be approximately 4-5 minutes before the material ofinterest 708 is advanced to the next cell.

In some embodiments, master control module 1350 may be configured tocontrol components and coordinate operation of components duringprocessing of the material of interest 708. Master control module 1350,also referred to as a master controller, main controller, or the like,may comprise one or more programmable logic controller (PLC),microprocessor, processor, computer, work station, laptop, server,and/or the like. Master control module 1350 may be electrically coupledto and/or be in communication with, without limitation, the conveyor1304, infeed door 1308, outfeed door 1310, DC power sources (e.g., DCpower sources 1320, 1330, 1340), RF generators (e.g., RF generators1322, 1332, 1342), stepper motors (e.g., stepper motors 1326, 1336,1346), compute device 1352, and compute device 1356 via the network1354. Master control module 1350 may be local or remote from the tunnel1302 and plurality of processing cells 1312.

Movement of conveyor 1304 (e.g., when to start moving, stop moving, rateof movement, amount of movement, etc.) may be dictated by signals fromthe master control module 1350. Infeed and outfeed doors 1308, 1310 maybe opened and closed based on signals generated by the master controlmodule 1350. DC power sources may be turned on and off and/or operatingparameters (e.g., power) specified by the master control module 1350.One or more of the DC power sources included in the plurality ofprocessing cells 1312 may be configured differently from each other fora given processing of a material of interest.

Master control module 1350 may have one or more communication lines orcouplings with each RF generator. For instance, one connection betweenthe master control module 1350 and a RF generator may comprise a controlline for the master control module 1350 to turn the RF generator on andoff and/or specify operating parameters. Another connection between themaster control module 1350 and the RF generator may comprise a monitorline in which the monitored reflected power level output of the RFgenerator (e.g., signal 320) may be received by the master controlmodule 1350. The received monitored reflected power levels associatedwith a particular cell may be used by the master control module 1350 tocontrol the stepper motor, and by extension select/adjust thecapacitance of the impedance matching module and the match impedance,for the particular cell. Instead of the stepper motor using thereflected power level detected by the RF generator to determine when tore-tune the capacitors in the impedance matching module as in system100, the master control module 1350 may provide such functionalities, asdescribed in greater detail below. Because the master control module1350 may be configured to use the reflected power level to control matchimpedance instead of the stepper motors, stepper motors (e.g., steppermotors 1325, 1335, 1346) need not include a control chip or logic orother determination capability mechanisms, in some embodiments.

Compute device 1352 may be located local to the tunnel 1302, in someembodiments. Compute device 1352 may comprise, without limitation, oneor more of a user interface, user control panel, computer, laptop, smartphone, tablet, Internet of Things (IoT) device, wired device, wirelessdevice, and/or the like which may be used by a user or operator tocontrol the system 1300. For example, the user may use compute device1352 to override the master control module 1350 (e.g., emergency shutdown, opening the infeed door 1308) or provide to inputs to be used bythe master control module 1350 (e.g., start temperature of the materialof interest 708) for efficient operation and/or configuration of thesystem 1300.

Compute device 1356 may be located remote from the tunnel 1302, in someembodiments. Compute device 1356 may comprise, without limitation, oneor more of a user interface, user control panel, computer, laptop, smartphone, tablet, Internet of Things (IoT) device, wired device, wirelessdevice, server, work station, and/or the like capable of at leastfunctionalities of the compute device 1352 and configured to provideadditional functionalities such as, but not limited to, data collection,data analytics, diagnostics, system upgrades, remote control, and/or thelike. Although not shown, compute device 1356 may also be incommunication with other tunnel systems. Compute device 1356 maycomprise one or more compute devices distributed over one or morelocations.

Compute device 1356 may communicate with the master control module 1350via the network 1354. Network 1354 may comprise a wired and/or wirelesscommunications network. Network 1354 may include one or more networkelements (not shown) to physically and/or logically connect computingdevices to exchange data with each other. In some embodiments, network1354 may be the Internet, a wide area network (WAN), a personal areanetwork (PAN), a local area network (LAN), a campus area network (CAN),a metropolitan area network (MAN), a virtual local area network (VLAN),a cellular network, a WiFi network, a WiMax network, and/or the like.Additionally, in some embodiments, network 1354 may be a private,public, and/or secure network, which may be used by a single entity(e.g., a business, school, government agency, household, person, and thelike). Although not shown, network 1354 may include, without limitation,servers, databases, switches, routers, firewalls, base stations,repeaters, software, firmware, intermediating servers, and/or othercomponents to facilitate communication.

In some embodiments, a plurality of materials of interest may besimultaneously processed in the tunnel 1302 at a given time. From one upto N materials of interest may be simultaneously processed in the tunnel1302, in which each of the materials of interest may be at a differenttemperature at each point in time since each is at a different point inits process.

FIG. 14 depicts a process 1400 that may be performed by the system 1300to thermally process the material of interest 708 initially positionedat the ith cell (e.g., just as the material of interest 708 electricallycouples with the ith electrode plate of the ith cell), according to someembodiments. The ith RF generator of the plurality of processing cells1312 may be configured to perform block 1402, which may be similar toblocks 1102-1112 of FIG. 11. As in block 1106 of FIG. 11, the monitoredreflected power level for the ith cell may be available as an output bythe ith RF generator, and which may be received by the master controlmodule 1350 at block 1430. Block 1430 may otherwise be similar to block1130.

Next, at block 1432, the master control module 1350 may be configured todetermine whether the received reflected power level exceeds a stepperthreshold. The stepper threshold may be similar to the threshold atblock 1132 except associated with adjusting the capacitance values ofthe ith impedance matching module. Block 1432 may otherwise be similarto block 1132. If the stepper threshold is not exceeded (no branch ofblock 1432), then process 1400 may return to block 1432 to continuemonitoring for a too high reflected power level. If the stepperthreshold is exceeded (yes branch of block 1432), then the mastercontrol module 1350 may be further configured to determine whether thematerial of interest 708 is at a temperature outside the temperaturerange associated with the ith cell. The reflected power level may becompared to an advancement threshold. The advancement threshold maycomprise a pre-determined threshold value that is larger than thestepper threshold value. For example, the advancement threshold may be 1V (e.g., approximately 35 W). Alternatively, the number of steps takenby the ith stepper motor and/or the physical state/positions of thevariable capacitors in the ith impedance matching module may be detectedand used by the master control module 1350 at block 1434 to determine(e.g., compared against a pre-determined value or state) whether thematerial of interest 708 has completed being processed in the ith celland is to be advanced to the next cell.

If the advancement threshold is not exceeded (no branch of block 1434),then process 1400 may proceed to block 1436, in which the master controlmodule 1350 may be configured to generate an adjustment signal. Thisadjustment signal may be similar to the adjustment signal generated inblock 1134. The adjustment signal may then be provided to and receivedby the ith stepper motor, at block 1438. In response, the ith steppermotor may be configured to actuate the ith stepper motor at block 1440.

The ith impedance matching module may respond to actuation of the ithstepper motor and process the RF output signal from the ith RF generatorat block 1404. Block 1404 may be similar to that described in connectionwith blocks 1136-1138 and 1114-1118 of FIG. 11. Likewise, the RF signaloutputted by the ith impedance matching module may be received by theith electrode plate at block 1406. Block 1406 may be similar to thosedescribed in connection with blocks 1120-1122 of FIG. 11. Once the(current) RF signal has been applied to the material of interest 708,process 1400 may be deemed to have returned to the operations associatedwith the ith RF generator for the next RF signal.

If the advancement threshold is exceeded (yes branch of block 1434),then process 1400 may proceed to block 1450. The master control module1350 may be configured to generate an advancement signal at block 1450.The advancement signal may comprise a signal to move or advance theconveyor 1304 by an amount needed to align or position the material ofinterest 708 to electrically couple with the next cell (the i+1 cell).

The advancement signal may be provided to and received by the conveyor1304 (or the mechanical movement mechanism associated with the conveyor1304), at block 1452. In response to receiving the advancement signal,actuation of conveyor 1304 may occur to move the conveyor 1304 indirection 1305 by the specified amount, at block 1454. With the materialof interest now moved to electrically couple with the next cell, i=i+1,at block 1456, and process 1400 may be repeated for the now incrementedith cell. Process 1400 may repeated as described herein for i=1 to Ncells.

In alternative embodiments where the conveyor 1304 may already beconfigured for continuous, incremental, indexed, or other such movementscheme, blocks 1450-1454 may be omitted. For example, conveyor 1304 maybe set to move incrementally by an amount sufficient for the material ofinterest 708 to advance to the next cell every 5 minutes. In such case,process 1400 may determine whether the time period allocated to the cellhas elapsed at the yes branch of block 1434. If the time period haselapsed, then process 1400 may proceed to block 145. Conversely if thetime period has not elapsed, process 1400 may return to block 1432.

FIG. 15 depicts a process 1500 that may be performed by the system 1300to thermally process the material of interest 708 initially positionedat the ith cell (e.g., just as the material of interest 708 iselectrically coupled with the ith electrode plate of the ith cell),according to alternative embodiments. Process 1500 may be similar toprocess 1400 except process 1500 is directed to operations when thecapacitors of the respective impedance matching modules may have fixedcapacitance values.

Blocks 1502 and 1530 may be similar to respective blocks 1402 and 1430of FIG. 14. Master control module 1350 may be configured to monitor thereceived reflected power level from the ith RF generator to determinewhether it exceeds an advancement threshold, at block 1534. Block 1534may be similar to block 1434. If the advancement threshold is notexceeded (no branch of block 1534), then process 1500 may return toblock 1534 to continue monitoring the latest received reflected powerlevel. Otherwise when the advancement threshold is exceeded (yes branchof block 1534), then master control module 1350 may be configured togenerate an advancement signal at block 1550. Block 1550 may be similarto block 1450. The advancement signal may be communicated to theconveyor 1304.

In response, conveyor 1304 may be configured to perform operations inblocks 1552, 1554, and 1556 which may be similar to respective blocks1452, 1454, and 1456. RF output signal provided by the ith RF generatormay be received by the ith impedance matching module at block 1504.Block 1504 may be similar to block 1404. RF signal outputted by the ithimpedance matching module may be received by the ith electrode plate atblock 1506. Block 1506 may be similar to block 1406.

As with process 1400, process 1500 may be repeated as needed for i=1 toN cells to continually thermally process the material of interest 708from a start, infeed, or incoming temperature to an end, outfeed, oroutgoing temperature using the plurality of processing cells 1312.

FIG. 16 depicts a process 1600 for endpoint detection techniques whichmay be performed by the system 100 and/or 1300, according to someembodiments. At block 1602, an endpoint detection associated signal maybe received. For system 100, such signal may be received by the controlmodule 314 included in the RF generator 104. Alternatively, such signalmay be received by an additional control module included in the system100. For system 1300, such signal may be associated with a particularcell and may be received by the master control module 1350. The endpointdetection associated signal may comprise one or more of, but not limitedto, a reflected power level indication (generated by the directionalcoupler included in the RF generator), a count of the number of stepstaken by the stepper motor (a counter may be maintained by the steppermotor and/or components commanding the stepper motor), an indication ofthe physical position or state of the variable capacitors included inthe impedance matching module (using optical sensors, such as lasers, tosense the physical position or state of the electrode plates of thevariable capacitors to determine the distance between the electrodeplates), and/or the like.

Next, the received endpoint detection associated signal may be analyzedto determine whether an endpoint has been reached at block 1604. In someembodiments, endpoint detection may refer to detecting a particularprocessing characteristic, temperature, or state of the material ofinterest 708. The particular processing characteristic, temperature, orstate of interest may be defined by a pre-determined threshold valuewhich may be compared against the endpoint detection associated signal.For system 100, the analysis may be performed by the control module 314included in the RF generator 104 and/or an additional control module(e.g., circuitry, microprocessor, etc.) included in the system 100. Forsystem 1300, the analysis may be performed by the master control module1350.

In embodiments where endpoint detection comprises detecting the materialof interest 708 having reached the desired end temperature (e.g.,endpoint temperature), the endpoint detection associated signal maycomprise the reflected power level. Because it is known that thematerial of interest 708 reaches the end temperature toward the latterpart of the processing time period, master control module 1350 may beconfigured to perform endpoint detection in the last cell (cell N) ofthe plurality of processing cells 1312 by looking for a particular valueof the reflected power level associated with the last cell (e.g., 65 W,70 W, 75 W, or at least 65 W). For system 100, endpoint detection maycomprise looking for a particular value of the reflected power levelwithin the latter time period (e.g., last 15 minutes or so or during alatent zone time period) of the expected processing time period.

When the endpoint detection associated signal comprises a count of thenumber of steps taken by the stepper motor, master control module 1350may be configured to monitor the step counter associated with thestepper motor included in the last cell until a particular count isreached. For system 100, the RF generator 104 and/or the additionalcontrol module included in the system 100 may also be configured tomonitor for a particular count in the step counter associated with thestepper motor 108. Because the steppe motor 108 in system 100 may stepthrough a greater number of steps due to the wider capacitance range forsystem 100 in comparison to the narrower capacitance range associatedwith the last cell for system 1300, the particular count values at whichendpoint may be deemed to have been reached may differ between systems100 and 1300.

When the endpoint detection associated signal comprises an indication ofthe physical position or state of the variable capacitors included inthe impedance matching module, master control module 1350 may beconfigured to monitor for a particular physical position or state of thevariable capacitors included in the last cell. For system 100, the RFgenerator 104 and/or additional control module included in the system100 may be configured to monitor for a particular physical position orstate of the variable capacitors included in the impedance matchingmodule 106. The particular physical positions or states of interest maybe different between the systems 100 and 1300.

In other embodiments, endpoint detection may comprise detection of whento advance the material of interest 708 to the next cell. Such detectionmay be similarly implemented as discussed above except the threshold orother reference characteristics against which the endpoint detectionassociated signal may be compared may be tailored to be cell specific.In still other embodiments, endpoint detection may comprise detection ofthe temperature of the material of interest 708. The reflected powerlevel, stepper counter value, and/or indication of the variablecapacitor physical position or state may correlate to the temperature ofthe material of interest 708. For example, the master control module1350 may configured to detect the actual start temperature of thematerial of interest 708 in the first cell (cell 1), which may bereferred to as start point detection.

As another example, if the material of interest 708 is expected to havea start temperature of −20° C. and the system 1300 is configured forsuch start temperature (e.g., cell 1 configured for processing between−20 to −17° C., cell 2 configured for processing between −16.9 to −14°C., etc.), but the material of interest 708 may have an actual starttemperature of −15° C., then when the material of interest is positionedat the first cell (cell 1) of system 1300, implementing endpointdetection at the first cell may permit detection of the immediate needto advance the material of interest 708 to the second cell (cell 2)since the material of interest 708 is already at a temperature lowerthan the temperatures associated with/being handled by the first cell.In such case, the material of interest 708 may spend less time at thefirst cell that nominally allocated for that cell. Alternatively, thefirst cell may be turned off so that no RF energy is provided by thefirst cell to that material of interest. If the second cell also hasendpoint detection capabilities, then once the material of interest 708has been positioned at the second cell, components associated with thesecond cell may detect that the material of interest 708 may beprocessed to heat from −15° C. to −14° C., rather than the fulltemperature range of from −16.9 to −14° C. configured for the secondcell. Thus, material of interest 708 may also spend less time thannominally allocated to be spent in the second cell.

If the endpoint is not detected (no branch of block 1604), then process1600 may return to bock 1604 to continue monitoring for the presence ofthe endpoint. Otherwise when the endpoint has been detected (yes branchof block 1604), then process 1600 may proceed to block 1606. At block1606, an appropriate response signal may be generated and transmitted.For example, if the endpoint detection comprises determining when to endprocessing of the material of interest 708 because a desired endtemperature has been reached, then the response signal may comprise asignal to shut down the RF generator 104, DC power source 102, and/orsystem 100. Likewise for system 1300, the response signal may comprise asignal to shut down one or more components included in the last cell, asignal to move the material of interest 708 out of the area associatedwith the last cell, or the like.

As another example, various thresholds for the reflected power level maybe used for power foldback protection, match impedance adjustment,and/or endpoint detection. For power foldback protection, the thresholdmay be 2.5 V (e.g., approximately 90 W) for a RF generator operating atup to 1250 W and the threshold may be 1.8 V (e.g., approximately 65 W)for a RF generator operating at up to 2000 W. For match impedanceadjustment, the (stepper) threshold may be set to 1 V (e.g.,approximately 35 W). For endpoint detection at which RF signal/energy tothe material of interest is halted, the threshold may be 1.8 V (e.g.,approximately 65 W) for a RF generator operating at up to 1250 W.

In some embodiments, for endpoint detection, even when the stepperthreshold may be exceeded, the capacitors may not be adjusted. Instead,the reflected power level may be intentionally allowed to increase, atleast during the latter time period of processing the material ofinterest, until a reflected power level of approximately 65 W isdetected. At this point in time, processing of the material of interestmay be stopped since reflected power level at approximately 65 Wcorresponds to the material of interest being at −3° C.±1° C.

In some embodiments, detection of the reflected power level may permitthe temperature of the material of interest to be known, in system 100and at each cell of system 100. The reflected power level may bemonitored to within 1% accuracy of a desired endpoint reflected powerlevel (e.g., 65 W) or to an accuracy of less than 1 W. Reflected powerlevel values may range between slightly higher than zero to 65 W, with65 W corresponding to −3° C. and about 10 W corresponding to −20° C.

In some embodiments, as the distance 716 increases between electrodeplates 702 and 704 (e.g., to process larger materials of interest), thecurrent at the second capacitor 810 (C2) may increase for a giventemperature of the material of interest. In order for the circuit 800,and in particular, the second capacitor 810 to be able to handle thehigher currents without exceeding the capacitor's current limitation,one or more additional capacitors may be provided in parallel withsecond capacitor 810 in circuit 800. For example, for a distance 716 ofapproximately 12 inches, three additional capacitors of 10 pF each maybe included in parallel with second capacitor 810.

Moreover, as distance 716 increases, capacitive reactance of thecapacitance 722 increases. In order for the circuit 800 to providematching impedance to the load, an increase in inductance associatedwith the transformer 808 may be required to match the increasedcapacitive reactance. For example, inductance of the each of the primaryand secondary windings of the transformer 808 may be 0.26 μH fordistance 716 of approximately 6 inches, 0.31 μH for distance 716 ofapproximately 8 inches, and 0.4 μH for distance 716 of approximately 12inches.

In some embodiments, a certain amount of reflected power level mayfacilitate a higher DC to RF power efficiency (e.g., up to 84 or 85%)than if the reflected power level is lowered by better matching theimpedance between the load and the RF generator. In other words,intentionally imperfect impedance match may increase the DC to RF powerefficiency to up to 84 or 85%. The table below shows various DC to RFpower efficiencies at different phase angles between the RF generatorand the load for a reflected power level of 6%, a reflection coefficientof the mismatch at 0.25, and a 1.7:1 voltage standing wave ratio (VSWR).

DC to RF Phase Forward Reflected Forward Load power angle power powerpower power Current Power efficiency (degrees) (in V) (in V) (W) (W) (A)dissipation (%) Initial 9.8 2.5 1220 1147 42 133 68 30 9.1 2.0 1078 101334 87 74 60 9.0 1.8 1080 1015 28 26 90 90 9.3 1.4 1220 1147 34 53 84 1208.5 1.8 1060 996 39 141 64 150 8.8 2.0 1100 1034 42 162 62

A phase angle of 90 degrees between the RF generator and the material ofinterest/load may be set, especially during the latent zone time period(the last portion of processing time when load temperature is at −5 to−3° C.), by controlling a length of the coaxial cable between the RFgenerator and electrodes coupling to the load. The resulting DC to RFpower efficiency may increase to 84% from approximately 75% (theefficiency under the matched impedance condition when reflected powermay be zero). A certain amount of reflected power results in a higherefficiency at some phase angles. A fixed match impedance may be used fora certain temperature range. The reflected power may be allowed to gofrom zero W to 75 W (6%) during the RF processing of the load. The fixedmatch and particular phase angle technique may be beneficial for loadswhose load impedance changes slowly over time. Loads in the latent zoneare examples of when the load impedance changes slowly over time. Thematch impedance and phase angle may be adjusted to achieve DC to RFpower efficiency higher than may be possible with a matched impedancebetween the RF generator and load. In some embodiments, a DC currentmeter coupled between the RF generator and DC power source along with apower meter coupled between the RF generator and the impedance matchingmodule may be used to optimize the phase angle, and in turn, the coaxialcable length, between the RF generator and load for increased DC to RFpower efficiency up to approximately 84 or 85%.

In this manner, monitored reflected power levels may be used to providepower foldback protection, to dynamically adjust match impedance, todetermine the load temperature during/throughout the RF application,and/or to determine when to end the RF signal applied to the load sincethe desired endpoint temperature has been reached.

Although certain embodiments have been illustrated and described hereinfor purposes of description, a wide variety of alternate and/orequivalent embodiments or implementations calculated to achieve the samepurposes may be substituted for the embodiments shown and describedwithout departing from the scope of the present disclosure. Thisapplication is intended to cover any adaptations or variations of theembodiments discussed herein. Therefore, it is manifestly intended thatembodiments described herein be limited only by the claims.

Illustrative examples of the devices, systems, and methods of variousembodiments disclosed herein are provided below. An embodiment of thedevices, systems, and methods may include any one or more, and anycombination of, the examples described below.

1. A system comprising:

a plurality of radio frequency (RF) generators;

a plurality of impedance match modules;

a plurality of electrode plates, first and second impedance matchmodules of the plurality of impedance match modules electrically coupledbetween respective first and second RF generators of the plurality of RFgenerators and respective first and second electrode plates of theplurality of electrode plates; and

a conveyor including a ground electrode,

wherein, when a load at a start temperature is to be placed on theconveyor, the system uses RF signals generated by the plurality of RFgenerators to cause the load to be at an end temperature different fromthe start temperature, wherein the conveyor is to position the load toelectrically couple to the first electrode plate during a first timeperiod and the first impedance match module is associated with a firstrange of temperatures between the start and end temperatures, andwherein the conveyor is to position the load to electrically couple tothe second electrode plate during a second time period and the secondimpedance match module is associated with a second range of temperaturesbetween the start and end temperatures that is different from the firstrange of temperatures.

2. The system of clause 1, further comprising a plurality of directcurrent (DC) power sources and a master control module, wherein firstand second DC power sources of the plurality of DC power sources areelectrically coupled to respectively the first and second RF generators,and wherein the master control module is in communication with the firstand second RF generators.

3. The system of clause 2, further comprising a plurality of steppermotors, wherein first and second stepper motors of the plurality ofstepper motors are electrically coupled to respectively the first andsecond impedance match modules, and wherein the master control module isin communication with the first and second stepper motors.

4. The system of claim 3, wherein the first impedance match moduleincludes variable capacitors, and wherein the first stepper motor, undercontrol by the master control module, changes a match impedanceassociated with the first impedance match module between the first RFgenerator and the load by changing a capacitance of the variablecapacitors.

5. The system of clause 2, wherein the master control module is to useindications of reflected power level provided by the first RF generatorto determine when to reposition the load from the first electrode plateto the second electrode plate.

6. The system of clause 2, wherein the first DC power source provides afirst DC signal to the first RF generator, and the first RF generatorconverts the first DC signal to a first RF signal having a DC to RFpower efficiency greater than 50%.

7. The system of clause 1, wherein the first impedance match module hasa first capacitance range different from a second capacitance range ofthe second impedance match module.

8. The system of clause 1, wherein the end temperature is between −4 to−2° Celsius (C), a temperature below 0° C., or a temperature below atwhich drip loss occurs for the load.

9. The system of clause 1, wherein the start temperature is lower thanthe end temperature.

10. The system of clause 1, wherein the first impedance match moduleincludes fixed or variable capacitors and capacitance values associatedwith the fixed or variable capacitors are selected for a first matchimpedance associated with the first impedance match module to match afirst load impedance associated with the load during the first timeperiod.

11. The system of clause 10, wherein the second impedance match moduleincludes second fixed or variable capacitors and capacitance valuesassociated with the second fixed or variable capacitors are selected fora second match impedance associated with the second impedance matchmodule to match a second load impedance associated with the load duringthe second time period, wherein the first and second load impedances aredifferent from each other.

12. The system of clause 1, wherein the plurality of electrode plates isdisposed above the conveyor and distributed along the length of theconveyor, and wherein a last electrode plate of the plurality ofelectrode plates is associated with causing the load to be at the endtemperature.

13. A method comprising:

positioning a load to electrically couple with a first electrode platefor a first time period, wherein a first impedance match module iselectrically coupled between the first electrode plate and a first radiofrequency (RF) generator, and wherein the first impedance match moduleis associated with a first range of temperatures between a starttemperature and an end temperature associated with the load;

applying a first RF signal to the load for a portion of the first timeperiod during which the load is at a temperature within the first rangeof temperatures, the first RF signal comprising a RF signal generated bythe first RF generator and impedance matched by the first impedancematch module;

positioning the load to electrically couple with a second electrodeplate for a second time period, wherein a second impedance match moduleis electrically coupled between the second electrode plate and a secondRF generator, and wherein the second impedance match module isassociated with a second range of temperatures between the start and endtemperatures different from the first range of temperatures; and

applying a second RF signal to the load for a portion of the second timeperiod during which the load is at a temperature within the second rangeof temperatures, the second RF signal comprising another RF signalgenerated by the second RF generator and impedance matched by the secondimpedance match module.

14. The method of clause 13, further comprising:

generating, by a first direct current (DC) power source, a first DCsignal and applying the first DC signal to drive the first RF generator;and

generating, by a second DC power source, a second DC signal and applyingthe second DC signal to device the second RF generator.

15. The method of clause 14, wherein the first RF signal comprises asignal having a DC to RF power efficiency of 75 to 80%, and wherein apower of the first RF signal is approximately up to 10 kiloWatt (kW).

16. The method of clause 13, further comprising:

receiving, from the first RF generator, an indication of a firstreflected power level associated with processing of the load using thefirst RF generator, impedance match module, and electrode plate;

determining whether the indication of the first reflected power levelexceeds a threshold; and

when the determination is affirmative, causing the load to be positionedto electrically couple with the second electrode plate.

17. The method of clause 16, wherein when the determination is negative,changing a first match impedance associated with the first impedancematch module, wherein the first match impedance is changed for the nextfirst reflected power level to be smaller than the first reflected powerlevel.

18. The method of clause 17, wherein changing the first match impedanceassociated with the first impedance match module comprises adjusting,using a first stepper motor, a capacitance of one or more variablecapacitors included in the first impedance match module.

19. The method of clause 13, wherein the start temperature is lower thanthe end temperature.

20. The method of clause 13, wherein the first impedance match moduleincludes fixed or variable capacitors and capacitance values associatedwith the fixed or variable capacitors are selected for a first matchimpedance associated with the first impedance match module to match afirst load impedance associated with the load during the first timeperiod.

21. The method of clause 20, wherein the second impedance match moduleincludes second fixed or variable capacitors and capacitance valuesassociated with the second fixed or variable capacitors are selected fora second match impedance associated with the second impedance matchmodule to match a second load impedance associated with the load duringthe second time period, wherein the first and second load impedances aredifferent from each other.

22. The method of clause 13, wherein the end temperature is between −4to −2° Celsius (C), a temperature below 0° C., or a temperature below atwhich drip loss occurs for the load, and wherein a total time period forthe load to heat from the start temperature to the end temperaturecomprises less than an hour.

23. The method of clause 13, wherein the load comprises protein,carbohydrates, foods, biologic material, fruits, vegetables, dairy,grains, or non-food materials.

24. An apparatus comprising:

means for positioning a load to electrically couple with a firstelectrode plate for a first time period, wherein a first means to matchimpedance is electrically coupled between the first electrode plate anda first radio frequency (RF) generator, and wherein the first means tomatch impedance is associated with a first range of temperatures betweena start temperature and an end temperature associated with the load;

means for applying a first RF signal to the load for a portion of thefirst time period during which the load is at a temperature within thefirst range of temperatures, the first RF signal comprising a RF signalgenerated by the first RF generator and impedance matched by the firstmeans to match impedance;

means for positioning the load to electrically couple with a secondelectrode plate for a second time period, wherein a second means tomatch impedance is electrically coupled between the second electrodeplate and a second RF generator, and wherein the second means to matchimpedance is associated with a second range of temperatures between thestart and end temperatures different from the first range oftemperatures; and

means for applying a second RF signal to the load for a portion of thesecond time period during which the load is at a temperature within thesecond range of temperatures, the second RF signal comprising another RFsignal generated by the second RF generator and impedance matched by thesecond means for matching impedance.

25. The apparatus of clause 24, further comprising:

means for generating a first DC signal and applying the first DC signalto drive the first RF generator; and

means for generating a second DC signal and applying the second DCsignal to device the second RF generator.

26. The apparatus of clause 24, wherein the first RF signal comprises asignal having a DC to RF power efficiency of 75 to 80%, and wherein apower of the first RF signal is up to approximately 10 kiloWatt (kW).

27. The apparatus of clause 24, further comprising:

means for receiving, from the first RF generator, an indication of afirst reflected power level associated with processing of the load usingthe first RF generator, means for matching impedance, and electrodeplate;

means for determining whether the indication of the first reflectedpower level exceeds a threshold; and

when the determination is affirmative, means for causing the load to bepositioned to electrically couple with the second electrode plate.

28. The apparatus of clause 27, wherein when the determination isnegative, means for changing a first match impedance associated with thefirst means for matching impedance, wherein the first match impedance ischanged for the next first reflected power level to be smaller than thefirst reflected power level.

29. The apparatus of clause 28, wherein the means for changing the firstmatch impedance associated with the first means for changing impedancecomprises means for adjusting a capacitance of one or more variablecapacitors included in the first means for matching impedance.

30. The apparatus of clause 24, wherein the end temperature is between−4 to −2° Celsius (C), a temperature below 0° C., or a temperature belowat which drip loss occurs for the load, and wherein a total time periodfor the load to heat from the start temperature to the end temperaturecomprises less than an hour.

31. A device comprising:

a first capacitor in parallel with an inductor;

primary windings of a transformer in series with the first capacitor andthe inductor; and

a second capacitor in series with secondary windings of the transformer,

wherein a radio frequency (RF) input signal is applied to the firstcapacitor and the primary windings of the transformer outputs a RFoutput signal, and wherein an impedance associated with the device is tomatch an impedance associated with a load in series with the device.

32. The device of clause 31, wherein the first and second capacitorscomprise variable capacitance capacitors.

33. The device of clause 31, wherein the first and second capacitorscomprise fixed capacitance capacitors.

34. The device of clause 31, further comprising one or more thirdcapacitors in parallel with the first or second capacitors.

35. The device of clause 31, wherein a capacitance associated with thefirst capacitor is approximately 16 to 250 picoFarad (pF).

36. The device of clause 31, wherein a capacitance associated with thesecond capacitor is approximately 16 to 80 picoFarad (pF).

37. The device of clause 31, wherein an inductance associated with theinductor is approximately 74 nanoHenry (nH).

38. The device of clause 31, wherein an inductance associated with theprimary windings of the transformer is approximately 0.26-0.28microHenry (μH) or approximately 0.31 μH.

39. The device of clause 31, wherein an inductance associated with thesecondary windings of the transformer is approximately 0.26-0.28microHenry (μH) or approximately 0.31 μH.

40. The device of clause 31, wherein the transformer comprises an aircore type of transformer.

41. An apparatus comprising:

a first capacitor in parallel with an inductor;

primary windings of a transformer in series with the first capacitor andthe inductor; and

a second capacitor in series with secondary windings of the transformer,

wherein the primary and secondary windings comprise flat conductivestrips, and the transformer comprises the primary windings wound aroundan outer circumferential surface of a tube and the secondary windingswound around an inner circumferential surface of the tube.

42. The apparatus of clause 41, wherein the tube comprises Teflon andhas dimensions to provide a coefficient of coupling of 0.76 for thetransformer.

43. The apparatus of clause 41, wherein the flat conductive strip ofrespective primary and secondary windings is 0.06 inch thick and 0.375inch wide.

44. The apparatus of clause 41, wherein the flat conductive strip ofrespective primary and secondary windings have the same length as eachother.

45. The apparatus of clause 41, wherein an inductance associated withthe primary or secondary windings of the transformer is approximately0.26-0.28 microHenry (μH) or approximately 0.31 μH.

46. The apparatus of clause 41, wherein the first and second capacitorscomprise variable capacitance capacitors or fixed capacitancecapacitors.

47. The apparatus of clause 41, further comprising one or more thirdcapacitors in parallel with the first or second capacitors.

48. The apparatus of clause 41, wherein a capacitance associated withthe first capacitor is approximately 16 to 250 picoFarad (pF).

49. The apparatus of clause 41, wherein a capacitance associated withthe second capacitor is approximately 16 to 80 picoFarad (pF).

50. The apparatus of clause 41, wherein an inductance associated withthe inductor is approximately 74 nanoHenry (nH).

51. A method comprising:

changing capacitance of one or both of first and second capacitorsincluded in an impedance match module in series between a radiofrequency (RF) generator and a load, wherein the change is initiated inaccordance with a first reflected power level, and wherein the firstcapacitor is in parallel with an inductor, primary windings of atransformer is in series with the first capacitor and the inductor, andthe second capacitor is in series with secondary windings of thetransformer; and

generating a RF output signal based on a RF signal received from the RFgenerator and in accordance with the changed capacitance of the firstand second capacitors in the impedance match module, wherein a secondreflected power level at a time after the first reflected power level isless than the first reflected power level.

52. The method of clause 51, wherein changing the capacitance compriseschanging a match impedance associated with the impedance match module toimprove matching a load impedance associated with the load.

53. The method of clause 51, wherein changing the capacitance isinitiated when the first reflected power level exceeds a threshold.

54. The method of clause 53, wherein the threshold is approximately 35Watt (W).

55. The method of clause 51, wherein the first reflected power level isdetected in the RF generator.

56. The method of clause 51, wherein the second capacitor comprises aplurality of capacitors in parallel with each other.

57. The method of clause 51, wherein changing the capacitance comprisesreducing the capacitance of one or both of the first and secondcapacitors.

58. The method of clause 51, wherein an inductance associated with theprimary or secondary windings of the transformer is approximately0.26-0.28 microHenry (μH) or approximately 0.31 μH, and an inductanceassociated with the inductor is approximately 74 nanoHenry (nH).

59. The method of clause 51, wherein a capacitance associated with thefirst capacitor is approximately 16 to 250 picoFarad (pF).

60. The apparatus of clause 51, wherein a capacitance associated withthe second capacitor is approximately 16 to 80 picoFarad (pF).

61. An apparatus comprising:

a control module;

an oscillator module that is to convert a direct current (DC) signalinto a radio frequency (RF) signal;

a power amplifier module coupled to an output of the oscillator module,the power amplifier module is to amplify a power associated with the RFsignal in accordance with a bias signal from the control module togenerate an amplified RF signal; and

a directional coupler module coupled to an output of the power amplifiermodule, the directional couple module is to detect at least a reflectedpower and to provide the detected reflected power to the control module,

wherein the control module is to generate the bias signal based on thedetected reflected power and is to provide the detected reflected poweras an available monitored output of the apparatus.

62. The apparatus of clause 61, wherein the oscillator module receivesthe DC signal from a DC power source, and the DC signal is at 42 Volt(V).

63. The apparatus of clause 61, wherein the power amplifier module is togenerate the amplified RF signal having a power range between 0 to 10kiloWatt (kW).

64. The apparatus of clause 61, wherein the power amplifier moduleincludes a plurality of laterally diffused metal oxide semiconductor(LDMOS) transistors arranged in a push-pull configuration.

65. The apparatus of clause 64, wherein a LDMOS transistor of theplurality of LDMOS transistors is to amplify a power of an input signalby approximately 30 decibel (dB).

66. The apparatus of clause 61, wherein the power amplifier moduleincludes a circuit having first and second branches at an input side andthe first and second branches combined at an output side, wherein thefirst and second branches are the same as each other.

67. The apparatus of clause 66, wherein the first branch includes aninput stage coupled to an input transformer stage, the input transformerstage coupled to a laterally diffused metal oxide semiconductor (LDMOS)transistor stage, the LDMOS transistor stage coupled to an outputtransformer stage, the output transformer stage coupled to a signalcombiner stage, and the signal combiner stage coupled to an outputstage, wherein the input stage receives the RF signal and the outputstage outputs the amplified RF signal.

68. The apparatus of clause 67, wherein the signal combiner stage andthe output stage are shared by the first and second branches.

69. The apparatus of clause 67, wherein the output transformer stageincludes a non-ferrite based transformer or a tube transformer usingpowdered iron toroids.

70. The apparatus of clause 67, wherein first and second impedancesassociated with respective first and second inputs of the signalcombiner stage excludes 25 Ohm (Ω).

71. The apparatus of clause 61, wherein the power amplifier module has aDC to RF power efficiency of 75 to 80% or greater than 50%.

72. The apparatus of clause 61, wherein the directional coupler modulecomprises a transformer type directional coupler and the directionalcoupler module is to provide the amplified RF signal as an RF outputsignal of the apparatus.

73. The apparatus of clause 72, wherein the RF output signal has afrequency of 27.12 MHz, 27 MHz, approximately 27 MHz, between 13 to 100MHz, or a RF frequency that is not a resonant frequency associated withan electrode structure providing the RF output signal to a load.

74. The apparatus of clause 61, wherein the directional coupler moduleis to detect a forward power and to provide the detected forward powerto the control module.

75. The apparatus of clause 61, wherein the control module is todetermine whether the detected reflected power exceeds a threshold.

76. The apparatus of clause 75, wherein when the threshold is exceeded,reduce the bias signal, wherein the threshold is associated with a softfoldback protection, and wherein the bias signal is a value greater thanzero.

77. The apparatus of clause 61, further comprising a voltage regulatormodule coupled to an input of the oscillator module, the voltageregulator module is to reduce a voltage associated with an input DCsignal received from a DC power source.

78. A method comprising:

converting a direct current (DC) signal into a radio frequency (RF)signal;

amplifying a power associated with the RF signal in accordance with abias signal from a control module to generate an amplified RF signal;

detecting at least a reflected power and providing the detectedreflected power to the control module; and

generating the bias signal based on the detected reflected power andproviding the detected reflected power as an available monitored output.

79. The method of clause 78, wherein amplifying the power associatedwith the RF signal comprises amplifying the RF signal to a power rangebetween 0 to 10 kiloWatt (kW).

80. The method of clause 78, wherein amplifying the power associatedwith the RF signal comprises amplifying the RF signal by approximately30 decibel (dB) using laterally diffused metal oxide semiconductor(LDMOS) transistors arranged in a push-pull configuration.

81. The method of clause 78, wherein amplifying the power associatedwith the RF signal comprises amplifying the RF signal to become theamplified RF signal at a DC to RF power efficiency of 75 to 80% orgreater than 50%.

82. The method of clause 78, further comprising detecting a forwardpower and providing the detected forward power to the control module.

83. The method of clause 78, further comprising determining whether thedetected reflected power exceeds a threshold.

84. The method of clause 83, wherein when the threshold is exceeded,reducing the bias signal by a particular amount, wherein the thresholdis associated with a soft foldback protection, and wherein the biassignal is a value greater than zero.

85. An apparatus comprising:

means for converting a direct current (DC) signal into a radio frequency(RF) signal;

means for amplifying a power associated with the RF signal in accordancewith a bias signal from a means for controlling to generate an amplifiedRF signal;

means for detecting at least a reflected power and providing thedetected reflected power to the means for controlling; and

means for generating the bias signal based on the detected reflectedpower and providing the detected reflected power as an availablemonitored output.

86. The apparatus of clause 85, wherein the means for amplifying thepower associated with the RF signal comprises means for amplifying theRF signal by approximately 30 decibel (dB) using laterally diffusedmetal oxide semiconductor (LDMOS) transistors arranged in a push-pullconfiguration.

87. The apparatus of clause 85, wherein the means for amplifying thepower associated with the RF signal comprises means for amplifying theRF signal to become the amplified RF signal at a DC to RF powerefficiency of 75 to 80% or greater than 50%.

88. The apparatus of clause 85, further comprising means for detecting aforward power and means for providing the detected forward power to themeans for controlling.

89. The apparatus of clause 88, further comprising means for determiningwhether the detected reflected power exceeds a threshold, and when thethreshold is exceeded, means for reducing the bias signal by aparticular amount to reduce an amount of amplification of the RF signalin the means for amplifying, wherein the bias signal is a value greaterthan zero.

90. The apparatus of clause 85, wherein the means for converting, meansfor amplifying, means for detecting, and means for generating areincluded in a first air tight compartment, wherein the means forconverting, means for amplifying, means for detecting, and means forgenerating are provided on respective printed circuit boards (PCBs)spaced apart from each other in the first air tight compartment, andfurther comprising a heat sink in contact with the respective PCBs, theheat sink at least partially located within a second air cooledcompartment adjacent to the first air tight compartment.

91. An apparatus comprising:

a radio frequency (RF) generator that is to generate a RF signal;

first and second electrodes; and

an impedance match module in series between the RF generator and thefirst electrode,

wherein the RF generator detects reflected power from the RF signalapplied to a load electrically coupled between the first and secondelectrodes to change a temperature of the load, the RF signal to beapplied to the load until the reflected power reaches a particularvalue.

92. The apparatus of clause 91, further comprising a direct current (DC)source that provides a DC signal to the RF generator, the RF generatorto generate the RF signal based on the DC signal, wherein the RF signalis at a frequency of 27.12 MHz, 27 MHz, approximately 27 MHz, or a RFfrequency that is not a resonant frequency associated with an electrodestructure providing the RF signal to the load.

93. The apparatus of clause 92, wherein the RF generator has associatedoutput impedance of 50 Ohm (Ω), and wherein the RF generator includeslaterally diffused metal oxide semiconductor (LDMOS) transistors andnon-ferrite based transformers to power amplify the DC signal.

93. The apparatus of clause 91, wherein the load comprises protein,carbohydrates, foods, biologic material, fruits, vegetables, dairy,grains, or non-food materials.

94. The apparatus of clause 91, wherein the impedance match moduleincludes a first capacitor in parallel with an inductor, primarywindings of a transformer in series with the first capacitor and theinductor, and a second capacitor in series with secondary windings ofthe transformer.

95. The apparatus of clause 91, wherein the RF signal is applied to theload to change the temperature of the load from a start temperature toan end temperature, wherein the end temperature is higher than the starttemperature, wherein the end temperature is between −4 to −2° Celsius(C), a temperature below 0° C., or a temperature below at which driploss occurs for the load.

96. The apparatus of clause 95, wherein the particular value is 65 Watt(W), 70 W, or 75 W, and when the RF signal is at the particular value,the temperature of the load is at the end temperature.

97. The apparatus of clause 91, wherein the apparatus comprises a firstcell of a plurality of cells, wherein the first cell is to change thetemperature of the load from a first temperature to a second temperatureduring a first time period, and a second cell of the plurality of cellsis to change to temperature of the load from the second temperature to athird temperature during a second time period, wherein the thirdtemperature is higher than the second temperature and the secondtemperature is higher than the first temperature.

98. The apparatus of clause 97, wherein a last cell of the plurality ofcells is to change the temperature of the load to an end temperaturethat is between −4 to −2° Celsius (C), a temperature below 0° C., or atemperature below at which drip loss occurs for the load.

99. The apparatus of clause 97, wherein the impedance match moduleincluded in the first cell includes variable capacitors tunable within afirst capacitance range associated with a temperature range between thefirst and second temperatures, and wherein a second impedance matchmodule included in the second cell includes variable capacitors tunablewithin a second capacitance range associated with the temperature rangebetween the second and third temperatures.

100. The apparatus of clause 99, wherein the second cell includes astepper motor coupled to the second impedance match module, the steppermotor is to change capacitance of capacitors included in the secondimpedance match module when the reflected power associated with thesecond cell exceeds a threshold smaller than the particular value.

101. The apparatus of clause 100, wherein the threshold is approximately35 W.

102. The apparatus of clause 91, further comprising a stepper motor thatis to receive the reflected power and, when the reflected power exceedsa threshold, the stepper motor is to change capacitance of capacitorsincluded in the impedance match module to change a match impedance ofthe impedance match module, wherein the threshold is smaller than theparticular value.

103. The apparatus of clause 102, wherein when a time duration of the RFsignal applied to the load is at least 30 minutes or the apparatuscomprises a last cell of a plurality of processing cells of the load,the capacitance of the capacitors included in the impedance match moduleis not changed when the threshold is exceeded.

104. The apparatus of clause 91, wherein, when the temperature of theload is within a latent zone from frozen to liquid, set a phase anglebetween the RF generator and the load to 90 degrees, and wherein a matchimpedance associated with the impedance match module is mismatched froma load impedance associated with the load.

105. The apparatus of clause 104, wherein a power efficiency of theapparatus when the temperature of the load is within the latent zone isapproximately 85%.

106. The apparatus of clause 91, wherein the RF generator is todetermine whether the reflected power exceeds a threshold, and when thethreshold is exceeded, reduce a power of the RF signal applied to theload.

107. The apparatus of clause 106, wherein the threshold is approximately90 Watt (W) for the RF generator that has a power range up to 1250 W.

108. The apparatus of clause 106, wherein the threshold is approximately65 Watt (W) for the RF generator that has a power range up to 2000 W.

109. The apparatus of clause 106, wherein the threshold is greater thanthe particular value, and wherein the RF generator reduces the power ofthe RF signal to a power level greater than zero Watt (W).

110. The apparatus of clause 91, wherein the RF generator is todetermine a temperature of the load based on the reflected power.

111. The apparatus of clause 110, wherein the RF generator is todetermine the temperature of the load to within a 1% accuracy of anactual temperature of the load.

112. A method comprising:

applying a radio frequency (RF) signal to a load;

monitoring a reflected power level associated with an apparatusincluding a direct current (DC) source, an impedance match module, aradio frequency (RF) generator, and the load; and

determining a temperature of the load based on the reflected powerlevel.

113. The method of clause 112, wherein monitoring the reflected powerlevel comprises monitoring the reflected power level to within 1%accuracy of an endpoint reflected power level or an accuracy of withinless than 1 Watt (W).

114. The method of clause 112, wherein applying the RF signal to theload comprises applying the RF signal to change the temperature of theload from a start temperature to an end temperature higher than thestart temperature.

115. The method of clause 114, wherein the end temperature is between −4to −2° Celsius (C), a temperature below 0° C., or a temperature below atwhich drip loss occurs for the load.

116. The method of clause 112, further comprising determining when tostop applying the RF signal to the load based on the reflected powerlevel.

117. The method of clause 116, wherein determining when to stop applyingthe RF signal comprises determining whether the reflected power level isat least 65 Watt (W).

118. The system of clause 1, wherein the conveyor moves continuously toposition the load from the first electrode plate to the second electrodeplate.

119. The system of clause 1, wherein the conveyor moves incrementally toposition the load from the first electrode plate to the second electrodeplate.

120. The system of clause 1, wherein the first RF generator is tomonitor a reflected power to determine a temperature of the load, thereflected power monitored to be accurate within 1% of an endpointreflected power level or have an accuracy of within less than 1 Watt(W).

121. The method of clause 13, wherein positioning the load toelectrically couple with the second electrode plate comprisescontinuously moving the load from the first electrode plate to thesecond electrode plate.

122. The method of clause 13, wherein positioning the load toelectrically couple with the second electrode plate comprises moving theload from the first electrode plate to the second electrode plate in astep motion.

123. The method of clause 13, further comprising:

monitoring a reflected power level associated with the load during thefirst time period; and

determining a temperature of the load based on the reflected powerlevel.

Although certain embodiments have been illustrated and described hereinfor purposes of description, a wide variety of alternate and/orequivalent embodiments or implementations calculated to achieve the samepurposes may be substituted for the embodiments shown and describedwithout departing from the scope of the present disclosure. Thisapplication is intended to cover any adaptations or variations of theembodiments discussed herein. Therefore, it is manifestly intended thatembodiments described herein be limited only by the claims.

We claim:
 1. A system comprising: a plurality of radio frequency (RF)generators; a plurality of impedance match modules; a plurality ofelectrode plates, a first impedance match module and a second impedancematch module of the plurality of impedance match modules beingelectrically coupled between a first RF generator and a second RFgenerator of the plurality of RF generators and a respective firstelectrode plate and a second electrode plate of the plurality ofelectrode plates; a plurality of direct current (DC) power sources and amaster control module, wherein a first power source and a second DCpower source of the plurality of DC power sources are electricallycoupled to respectively the first RF generator and the second RFgenerator, and wherein the master control module is in communicationwith the first RF generator and the second RF generator; and a conveyorincluding a ground electrode, wherein, when a load at a starttemperature is to be placed on the conveyor, the system uses RF signalsgenerated by the plurality of RF generators to cause the load to be atan end temperature different from the start temperature, wherein theconveyor is to position the load to electrically couple to the firstelectrode plate during a first time period and the first impedance matchmodule is associated with a first range of temperatures between thestart and end temperatures, and wherein the conveyor is to position theload to electrically couple to the second electrode plate during asecond time period and the second impedance match module is associatedwith a second range of temperatures between the start and endtemperatures that is different from the first range of temperatures. 2.The system of claim 1, further comprising a plurality of stepper motors,wherein first and second stepper motors of the plurality of steppermotors are electrically coupled to respectively the first and secondimpedance match modules, and wherein the master control module is incommunication with the first and second stepper motors.
 3. The system ofclaim 2, wherein the first impedance match module includes variablecapacitors, and wherein the first stepper motor, under control by themaster control module, changes a match impedance associated with thefirst impedance match module between the first RF generator and the loadby changing a capacitance of the variable capacitors.
 4. The system ofclaim 1, wherein the master control module is to use indications ofreflected power level provided by the first RF generator to determinewhen to reposition the load from the first electrode plate to the secondelectrode plate.
 5. The system of claim 1, wherein the first DC powersource provides a first DC signal to the first RF generator, and thefirst RF generator converts the first DC signal to a first RF signalhaving a DC to RF power efficiency greater than 50%.
 6. The system ofclaim 1, wherein the first impedance match module has a firstcapacitance range different from a second capacitance range of thesecond impedance match module.
 7. The system of claim 1, wherein the endtemperature is between −4 to −2° Celsius (C), a temperature below 0° C.,or a temperature below at which drip loss occurs for the load.
 8. Thesystem of claim 1, wherein the start temperature is lower than the endtemperature.
 9. The system of claim 1, wherein the first impedance matchmodule includes fixed or variable capacitors and capacitance valuesassociated with the fixed or variable capacitors are selected for afirst match impedance associated with the first impedance match moduleto match a first load impedance associated with the load during thefirst time period.
 10. The system of claim 9, wherein the secondimpedance match module includes second fixed or variable capacitors andcapacitance values associated with the second fixed or variablecapacitors are selected for a second match impedance associated with thesecond impedance match module to match a second load impedanceassociated with the load during the second time period, wherein thefirst and second load impedances are different from each other.
 11. Thesystem of claim 1, wherein the plurality of electrode plates is disposedabove the conveyor and distributed along the length of the conveyor, andwherein a last electrode plate of the plurality of electrode plates isassociated with causing the load to be at the end temperature.
 12. Thesystem of claim 1, wherein the conveyor moves continuously to positionthe load from the first electrode plate to the second electrode plate.13. The system of claim 1, wherein the conveyor moves incrementally toposition the load from the first electrode plate to the second electrodeplate.
 14. An apparatus comprising: means for positioning a load toelectrically couple with a first electrode plate for a first timeperiod, wherein a first means to match impedance is electrically coupledbetween the first electrode plate and a first radio frequency (RF)generator, and wherein the first means to match impedance is associatedwith a first range of temperatures between a start temperature and anend temperature associated with the load; means for applying a first RFsignal to the load for a portion of the first time period during whichthe load is at a temperature within the first range of temperatures, thefirst RF signal comprising a RF signal generated by the first radiofrequency RF generator and impedance matched by the first means to matchimpedance; means for positioning the load to electrically couple with asecond electrode plate for a second time period, wherein a second meansto match impedance is electrically coupled between the second electrodeplate and a second RF generator, and wherein the second means to matchimpedance is associated with a second range of temperatures between thestart and end temperatures different from the first range oftemperatures; and means for applying a second RF signal to the load fora portion of the second time period during which the load is at atemperature within the second range of temperatures, the second RFsignal comprising another RF signal generated by the second RF generatorand impedance matched by the second means for matching impedance. 15.The apparatus of claim 14, further comprising: means for generating afirst DC signal and applying the first DC signal to drive the first RFgenerator; and means for generating a second DC signal and applying thesecond DC signal to device the second RF generator.
 16. The apparatus ofclaim 14, wherein the first RF signal comprises a signal having a DC toRF power efficiency of 75 to 80%, and wherein a power of the first RFsignal is up to approximately 10 kiloWatt (kW).
 17. The apparatus ofclaim 14, further comprising: means for receiving, from the first radiofrequency RF generator, an indication of a first reflected power levelassociated with processing of the load using the first RF generator,means for matching impedance, and electrode plate; means for determiningwhether the indication of the first reflected power level exceeds athreshold; and when the determination is affirmative, means for causingthe load to be positioned to electrically couple with the secondelectrode plate.
 18. The apparatus of claim 17, wherein when thedetermination is negative, means for changing a first match impedanceassociated with the first means for matching impedance, wherein thefirst match impedance is changed for the next first reflected powerlevel to be smaller than the first reflected power level.
 19. Theapparatus of claim 18, wherein the means for changing the first matchimpedance associated with the first means for changing impedancecomprises means for adjusting a capacitance of one or more variablecapacitors included in the first means for matching impedance.
 20. Theapparatus of claim 14, wherein the end temperature is between −4 to −2°Celsius (C), a temperature below 0° C., or a temperature below at whichdrip loss occurs for the load, and wherein a total time period for theload to heat from the start temperature to the end temperature comprisesless than an hour.